MITH’S'  ILLUSTRATED  ASTRONOMY 


rwr,  sd  I'FXEScopii:  in  size  in  thf  united  states,  at  the  Cincinnati  observai  ouv 


N t ro  - ^ d r k : 

DANIEL  BUKGESS'&  CO.,  60  JOHN.STREET 

(LATE  CADy  <fe  BURGESS.^ 


Return  this  book  on  or  before  the 
Latest  Date  stamped  below. 

Theft,  mutilation,  and  underlining  of  books 
are  reasons  for  disciplinary  action  and  may 
result  in  dismissal  from  the  University, 
University  of  Illinois  Library 


THE  LARGEST  TELESGUPES  [N  THE  WORLD 
Lord  Hoskk’s  Telescope,  at  Birr  Castle,  Ireland,  36  feet  in  lenRth. 

>>iR  Wm.  Hkrsciiki/s  do.  at  Greenwich,  London,  -It)  do.  inleiu'th  (not  muse  ) 

J lie  Dorpat  1 cleseope,  at  Dorpnt  (K.u.ssia,')  Prof.  Strovb,  16  “ 

Sir  .mhrs  Soi.'Tii's 'J’eh'scope  at  Imndon,  1!)  “ 

Cirieirinali  'I’clescope,  (Ohio,)  PitoF.  MirciiRi,,  17  “ 

'I’elescopc  at  O.mihridgc,  Ma.ss  2B  “ 


t'-imher  cTll'yh-Tr^nrlicih^  wtierjevi-r  a leaeon  i»  /(iven  to  a class,  that  the 

<U  r A I'- 'll'- and  exi.lain,  if  necessary,  the 

UiaaX  su  I'T"""  I','  "I"'"'  tineMlonini:  the  whole  class 

l.k  "f  y oues  onVrel^  m^  pnpd,  who  does  „„l  fully  underslanil  (he  snhjecl  to 

he  IS  Jur;,/;  r.  il,  ;; ' '’'■.'T'"'-  "i-  impii.  when 

i.vrn  7 . ;e^  ;:,u o 'ri  "''■[.••'-'f-r  wincoudue  himseif  soieiy  to  ,he  ,,ne'7':uH 
''lii'  h sv  I «d  die  o . 6^^  wil  ask  many  which  may  occur  to  him  at  (h  it  lime,  am, 


HINTS  TO  TEAOHEnS. 


He  would  also  particularly  recommend,  that  the  teacher  when  henriii!;  a recitation, 
chance  the  (|uestion  or  put  it  in  a dilfcrent  form,  in  all  cases  where  it  will  admit  of  it 
r or  example : 

What  is  (he  adraction,  hy  which  all  particles  of  matter  tend  toward  each  othei3 
cajlcdr  The  altracdon  of  gravitalion. 

Wha(  is  (he  adraction  o(  gnivitalion  I It  is  that  attraction  by  which  all  particlc.s  of 
milder  lend  toward  each  other. 


"^ha(  i.s  (he  point  in  (he  heavens  directly  over  our  heads  called  I 'I'he  z 
VV  iiiii  IS  he  zenith  1 It  is  that  point  in  the  heavens  directly  over  one  lie 


zemtn. 

iieads 


(REVISED  AND  ENLARGED.) 


SMITH’S 


ILLUSTRATED 

STRONOM  Y, 


DESIGNED  FOR  THE  USE  OF  THE 


PUBI^IC  OR  COMMON  SCHOOLS 

O THE  UIITED  STATES. 


ILLUSTRATED  WITH 


NUMEROUS  ORIGINAL  DIAGRAMS. 


BY  ASA  SMITH. 


Principal  of  Public  School  No.  12,  City  of  New  Yc.'k. 


• NINETEENTH  EDITION. 

Ncto-JJork: 

DANIEL  BURGESS  & CO.,  60  JOHN. STREET. 


1 8 5 6. 


I L L U S T R A r K I)  A S 'I'  R ()  N ()  M Y , 


C 0 N T E N T S. 


Lesson 

1.  Vague  ideas  of  the  Ancients  respecting  the  Shape  of  the  Earth, 

“ Ptolemaic  System,  ...... 

2,  3.  Introduction  to  Astronomy,  . . . . . 

4,  5,  6.  Astronomy,  Solar  System,  &c.  .... 

7.  Diameters,  Magnitudes,  Distances  and  Revolutions  of  the  Sun  and 

Planets,  - - . - 

8.  Centripetal  and  Centrifugal  Forces,  . . . . . 

9.  Kepler’s  Laws, 

“ Mean  and  True  Place  of  a Planet — Aphelion  and  Perihelion,  - 

10.  Mean  and  True  Motion  of  a Planet,  .... 

11,  12.  The  Sun ; Spots  on  the  Sun,  . . . . . 

13.  Transits  of  Mercury  and  Venus,  .... 

14.  Zodiac;  Constellations  of  the  Zodiac,  . . . . 

15.  Apparent  Motion  of  the  Sun  in  the  Heavens,  ... 

16.  Signs  of  the  Ecliptic,  &c.  ...... 

17.  The  Planet  Mercury,  ...... 

18.  The  Planet  Venus,  ....... 

19.  Seasons  at  Venus,  Phases,  &c.  ..... 

20.  21,22.  Earth,  Definitions,  &c.  . . . . . 

23,  24,  25.  Earth  and  Seasons,  Equinoxes,  &c. 

— Aerolites,  Meteors,  &c.  ...... 

26,  27.  Mars,  Asteroids,  ...... 

28,  Jupiter,  Saturn’s  Rings,  - - 

29,  30.  The  Planet  Saturn,  ...  . . 

31.  The  Planet  Herschel,  or  Uranus,  . . . . . 

32.  The  Planet  Leverrier,  or  Neptune,  - . 

33.  The  Moon  ; Phases  of  the  Moon,  ..... 


rage. 

7 

7 

7 

9 

9 
11 
11 
11 
11 
13 
13 
15 
15 
15 
17 
17 
17 
19 
21 
23 
25 
27 
29 
31 
, 31 
33 


LcAson,  Pn^A, 

34,  35.  The  Moon — (continued) — Physical  Constitution  of  the  Moon,  - 35 

36.  Eclipses,  - - . . - . . 38  40 

37,  38,  Moon’s  Nodes,  Inferior  and  Superior  Conjunction,  - - 42 

39.  Inferior  and  Superior  Planets,  - - - . - 42 

40.  Greatest  Number  of  Eclipses  in  a year,  ....  44 

41.  42.  Tides,  - - - - . - . - 46 

43,  44.  Orbits  of  the  Planets  and  Comets ; Comets,  . . - 48  50 

45.  Atmosphere,  - . . . - . - 52 

46.  Refraction,  .......  52 

47.  Parallax,  - - . - - . . -52 

48.  Light  and  Heat,  52 

49.  Terrestrial  and  Celestial  Globes,  - - - - - 54 

50.  51.  General  Definitions  respecting  the  Globes,  . - - 54 

52.  Fixed  Stars ; Distance  to  the  nearest  Fixed  Star,  - - .56 

53.  Our  own  Cluster  or  Firmament  of  Stars,  Motions  of  the  Stars,  Multiple 

Stars,  Binary  Systems,  - - - . - - 56 

54.  Nebulae,  Number,  Distance,  &c. ; Origin  of  the  Solar  System,  - 58 

— An  Explanation  of  Leap  Year,  - - . - 64 

— Equation  of  Time,  ......  54 

— To  find  the  Magnitudes  of  the  Planets,  - - - - 68 

— To  find  the  distances  of  the  Planets  from  the  Sun,  ...  68 

— Zodiacal  Light,  - - - - - . -72 

— To  find  the  circumference  of  the  Earth,  ...  - 72 

— Problems  on  the  Terrestrial  Globe,  - - - - - 76 

— Problems  on  the  Celestial  Globe,  . - - . - 77 

— Glossary  or  Explanation  of  Astronomical  Terms,  - - 78-79 


ILLUSTRATIONS. 


Orrery,  with  a view  of  the  Solar  System  in  the  back  ground,  - - 6 

Solar  System  and  Comparative  Magnitudes,  ...  8 

Centripetal  and  Centrifugal  force,  - - - - 1 0 

Kepler’s  Laws,  - - ■ - - - - 10 

The  Mean  and  True  Place  of  a Planet,  - - - - 10 

Circle;  Eclipse;  Concentric  Circles ; Circles  not  in  the  same  plane,  - 10 

Cut  Section  of  the  Sun,  - - - - - 12 

Spots  on  the  Sun,  -----  12 

Transits  to  the  year  1900,  - - - - - 12 

Signs  of  the  Zodiac,  - - - - - 14 

Mercury  and  Venus;  Telescopic  Views;  Venus  Morning  and  Evening  Star,  16 
EaKh  and  Definitions,  - - - - - 1 8 

Sea-sons;  Summer  and  Winter  Rays,  Equinoctial  and  Solstitial  Points,  - 20 
Aerolites  and  Meteors,  - - - - - 22 

Mars,  Asteroids  and  Jupiter,  - - - - - 24 

Jupiter;  Telescopic  Views,  &c.  - - - - 26 

Saturn ; Saturn’s  Rings  and  Moons,  - - - - 28 


Herschel  and  Leverrier,  - - - - - 30 

Phases  of  the  Moon  ; Apparent  Magnitude  of  the  Sun  and  Moon,  - 32 

Telescopic  View  of  the  New  Moon,  - - - - 34 

Telescopic  View  of  the  Full  Moon,  - - - - 36 

Telescopic  View  of  the  Old  Moon,  - - - - 37 

Eclipses,  .....  39-41 

Moon’s  Nodes ; Inferior  and  Superior  Conjunction,  - - 43 

Inferior  and  Superior  Planets ; Heliocentric  Longitude,  - - 43 

Greatest  Number  of  Eclipses  that  can  happen  in  a year,  - - 45 

Tides,  and  Moon-light  at  the  Poles,  - - - - 47 

Orbits  of  the  Planets  and  Comets ; Comets,  ...  49-51 

Refraction ; Parallax  Light  and  Heat,  - . . - 53 

View  of  the  Earth’s  Orbit,  as  seen  from  the  nearest  fixed  Star,  - 53 

Terrestrial  and  Celestial  Globes,  and  Milky-way,  - - - 55 

Binary  Systems ; Quadruple  Stars,  - - - - 57 

A Perpendicular  and  an  Oblique  View  of  our  own  Cluster  or  Firmament,  57 
Telescopic  Views  of  remarkable  Nebulae  and  Cluster  of  Stars,  - - 59 


SIDEREAL  MAPS. 


Description  and  use  of  the  Sidereal  Maps,  - - - 60 

Explanations,  showing  the  manner  of  using  the  Maps,  - 60 

Ibrections  for  finding  the  North  Star  at  any  time,  - - 60 

Descrijition  of  the  Constellations  visible  from  January  21sl  to  April  17th,  61 

Princijial  Stars  visible,  and  Times  for  Observation,  from  January  21st  to 

April  17th,  - - - - 62 

Map  of  the  Visible  Heavens,  from  January  2l8t  to  April  17th  - 63 

Ilescriptions  of  the  Constellations  visible  from  April  18th  to  July  21st.  65 


Principal  Stars  visible,  and  Times  for  tlbservation,  from  April  ISthtoJiily  21st.  66 


Map  of  the  Visible  Heavens,  from  April  18th  to  July  21st.  - - 67 

De.scriptions  of  the  Constellations  visible,  from  July  22d  to  October  31st.  69 

Principal  Stars  visible,  and  Times  for  Observation,  from  July  22d  to  Octo- 
ber 31st.  - - - - 70 

Maj)  of  the  Visible  Heavens,  from  July  22d  to  October  31st.  - - 71 

Descrijjtions  of  the  Constellations  visible,  from  November  1st  to  January  20th.  73 
Principal  Stars  visible,  and  Times  for  Observation,  from  November  1st  to 

January  20th.  - - - - 74 

Map  of  the  Visible  Heavens,  from  November  1st  to  January  20th.  - 75 


F,nUr*4  acr,or4lng  to  Act  of  Congrnii,  In  llio  yunr  ISIS,  by  .\i»  S,MrTii,  In  tbo  (Ucrli’t  Olltro  of  Iho  District  Court  of  tho  United  States,  for  tlie  Southern  District  of  New  York. 


VIWCRWT  L.  DILL. 

IM  rulfoo  ntrmikK.  T 


O A.  ALVORD,  PRINIER 


<D 


L 

to 


5"^  3 

P It  E F A C E 

REE50  i 1-  -3  l ‘ w-V\3i-^  Q THE  REVISED  EDITION. 

Nearly  six  yeare  have  elapsed  since  the  publication  of  this  Illustrated  Astronomy  ; during  this  time  many  new  planets  or  Asteroids  have  been 
discovered ; a notice  of  which  will  be  found  in  its  proper  place ; also  a notice  of  Professor  Bond’s  new  tlieory  in  regard  to  Saturn’s  rings. 

The  favor  with  which  this  work  has  been  received  by  teachers  and  the  public  generally  has  far  exceeded  the  author’s  expectations,  it  having  run 
through  fifteen  Editions  since  its  publication.  It  has  been  thoroughly  revised,  and  the  new  discoveries  are  brought  up  to  the  present  date ; five  new 
illustrations  have  been  added  and  a new  set  of  Electrotype  plates  have  been  procured  at  a great  expense,  which  give  a very  distinct  and  beautiful  diagram. 

It  has  been  the  object  of  the  author  of  this  Illustrated  Astronomy,  to  present  all  the  distinguishing  principles  in  physical  Astronomy  with  as 
few  words  as  possible ; but  with  such  occular  demonstrations,  by  way  of  diagrams  and  maps,  as  shall  make  the  subject  easily  understood.  The 
letter  press  descriptions  and  the  illustrations  will  invariably  be  found  at  the  same  opening  of  the  book ; and  more  explanatory  cuts  are  given,  and  at  a 
much  less  price  than  have  been  given  in  any  other  elementary  Astronomy. 

This  work  is  designed  for  common  schools,  but  may  be  used  with  advantage  as  an  introductory  work  in  high-schools  and  academies.  In  the  prepa- 
ration of  these  pages  most  of  the  best  works  in  our  language  have  been  consulted,  and  the  best  standard  authorities,  with  regard  to  new  discoveries 
and  fiicts,  have  governed  the  author’s  decisions. 

The  Diagrams,  which  are  larger  and  more  full  than  those  of  any  other  work  adapted  to  common  schools,  are  most  of  them  original  in  their 
design,  and  exhibit  the  positions  and  phases  of  the  planets  in  their  orbits.  The  drawings  being  upon  the  principal  of  perspective,  exhibit  the  in- 
clinations of  their  several  axes  to  the  planes  of  their  orbits  more  correctly  than  has  hitherto  been  done  in  any  other  popular  work.  It  is  well  to 
intimate  to  the  young  elementary  student,  who  has  made  himself  some  what  acquainted  with  the  sublime  mechanism  of  the  solar  system,  that 
there  is  something  more  magnificent  beyond.  Accordingly  the  author  has  given  a few  Sidereal  Maps,  just  to  awaken  in  the  young  astronomer  the 
amazing  conception,  that  unnumbered  suns  and  revolving  worlds  occupy  the  depths  of  space  far  beyond  the  confines  of  our  planetary  system.  By 
these  maps  he  will  be  able  to  learn  the  relative  positions  of  the  principal  constellations  and  stars,  which  will  be  found  useful  and  interesting  to  him 
in  subsequent  investigations  of  the  ennobling  truths  of  mathematical  Astronomy. 

The  author  is  not  so  vain  as  to  suppose  that  he  has  been  able  to  present  to  teachers  a faultless  work  ; but  in  his  own  practice,  finding  it  tedious 
and  often  difficult  to  explain  all  the  representable  phenomena  of  the  science  on  the  black-board,  and  finding  also  a general  concurrence  of  opinion 
among  teachers  most  interested  in  the  study  of  Astronomy,  that  a clieap,  compact,  and  illustrated  work  is  necessary  in  our  common  schools,  he  has 
attempted  the  production  of  such  a work.  The  success  of  the  work  and  the  favor  with  which  it  has  been  received,  sufficiently  prove  its  superiority  over 
all  other  works  for  the  instruction  of  pupils  in  the  general  outlines  of  the  science  of  Astronomy,  and  satisfies  the  author  that  he  has  not  labored  in 
vain  in  the  production  of  this  work. 

Objections  which  are  sometimes  urged  against  questions  and  answers,  in  an  elementary  work,  will  not,  the  Author  hopes,  be  urged  in  this  case,  as 
the  pupil  has  the  subject,  fully  illustrated,  continually  before  the  eye,  while  he  is  learning  his  lesson. 

To  the  Teachers,  of  our  common  country,  this  work  is  most  respectfully  dedicated,  in  the  sincere  desire  that  the  cause  of  education  may  be 
benefitted,  and  the  labors  of  instruction  in  Astronomy  may  be  rendered  more  easy  and  pleasant,  from  the  illustrations  it  contains. 

ASA  SMITH,  Principal  of  Ward  School  No.  11,  {Late  Public  School,  Wo.  12,) 

Seventeenth  Street,  near  Eighth  Avenue,  City  of  New  York. 


NAMES  AND  CHARACTERS  OF  THE  SIGNS,  PLANETS,  AND  ASPECTS. 


Aries, 

- T 

Sagittarius  - 

- ^ 

Earth, 

e 

Hebe,*  - - 

- 

Quartile, 

□ 

Taurus,  - 

Capricornus, 

- VS 

Mars, 

c? 

Iris,* 

- 

Trine, 

Opposition,  - 

A 

Gemini, 

- n 

Aquarius, 

Vesta, 

fi 

Jupiter, 

- n 

<? 

Cancer,  - 

Pisces, 

Juno, 

0 

Saturn, 

h 

Ascending  Node, 

S2 

Leo,  - 

• s\ 

Sun, 

© or  o 

Ceres, 

? ■ 

Herschel, 

- w 

Descending  Node, 

2§ 

Virgo,  - 
Libra, 
Scorpio,  - 

UJ? 

- . JV 

Moon,  ® 

Mercury, 

Venus, 

O ® ® 

- 0 

Pallas, 

$ 

Leverrier,  - 

- (I) 

- 6 

Astraea,* 

Conjunction, 

Sextile, 

ta 

- ? 

Flora,*  - 

* 

* Not  determined. 


The  following  is  a list  of  the  names  of  the  new  Asteroids,  date  of  discovery,  and  by  whom  discovered, 


Name  and  Number. 

Date  of  Discovery 

Name  of  Discoverer. 

Name  and  Number. 

Date  of  Discovery 

Name  of  Discoverer. 

1.  Ceres 

2.  Pallas 

3.  Juno 

4.  Vesta 

5.  Astrsea 

6.  Hebe 

7.  Iris 

8.  Flora 

9.  Metis 

10.  Hygeia 

11.  Parthenope 

12.  Victoria 

1800,  Jan.  1. 
1802,  Mar.  28. 
1804,  Sept.  1. 
1807,  Mar.  29. 
1845,  Dec.  8. 
1847,  July  1. 
1847,  Aug.  13. 

1847,  Oct.  18. 

1848,  April  26. 

1849,  April  12. 

1850,  May  11. 
1850,  Sept.  13. 

Piazza,  of  Sicily. 

Olbers,  of  Bremen. 
Harding. 

Olbers. 

Hencke,  of  Germany. 
Hencke. 

Hind,  of  London. 

Hind. 

Graham,  of  Ireland. 

De  Gasparis,  of  Naples. 

De  Gasparis. 

Hind. 

13.  Egeria 

14.  Irene.. .......... 

15.  Eunoinia 

16.  Psyche 

17.  Thetis 

18.  Melpomene 

1 9.  Fortuna 

20.  Massilia.. ........ 

21.  Lutetia. 

22.  Calliope 

23.  Thalia 

1850,  Nov.  2. 

1851,  May  19. 

1851,  July  29. 

1852,  Mar.  17. 
1852,  April  17. 
1852,  June  24. 
1852,  Aug.  22. 
1852,  Sept.  22. 
1852,  Nov.  15. 
1852,  Nov.  16. 
1852,  Dec.  15. 

De  Gasparis. 

Hind. 

De  Gasparis. 

De  Gasparis. 

Luther,  of  Germany. 

Hind. 

Hind. 

De  Gasparis. 

Goldschmidt,  of  Germany. 
Hind. 

Hind. 

Aca 


1 

INTRODUCTION  TO  ASTRONOMY. 


LESSON  I . 

Question.  What  is  the  bo(iy  cal!<'d  upon  which  we  live? 

Ansicer.  It  is  called  the  Eakth,  or  World. 

Q.  What  idea  had  the  Ancients  respecting  the  shape  of  the  earth  ? 

A.  They  believed  it  was  an  exteti-sive  plain,  rendered 
uneven  by  hills  and  mountains. 

Q.  Why  did  they  think  it  was  an  extended  plxin  ? 

A.  Becau.se  they  formed  their  opinions  from  appear- 
ances only. 

Q.  Did  they  lielieve  that  the  earth  had  any  motion  1 

A.  They  did  not;  they  believed  that  the  earth  rested 
on  a solid,  immovable  foundation. 

[Thev  very  naturally  came  to  this  conclusion,  as  they  were  entirely  ignorant  of  the  laws  of 
attraction  or  gravitation.  They  believed  that  if  the  earth  were  to  turn  over,  that  every  thing 
would  be  precipitated  from  its  surface.] 

Q.  Had  they  any  definite  ideas  respecting  what  held  the  earth  up  ? 

A.  Their  views  were  very  vague  and  unsatisfactory. 

[There  have  been  many  absurd  ideas  advanced,  at  diftcrent  aeres  of  the  world,  as  to  what  sup- 
ported the  earth  Some  supposed  it  to  be  shaped  like  a Casoe,  and  to  float  upon  the  waters  ; o'hers, 
lliat  it  rested  upon  the  liack  of  an  K,i.KPH,vr,  or  huge  Ti  rti.k  ; while,  according  to  mythology. 
Atlas  supi>orted  it  upon  his  shoulders  : hut,  what  kept  the  waters  in  their  plare,  or  upon  what  the 
Elephant,  Turtle,  or  Atlas  stood— this  was  a mystery  they  coui  o nevkr  solve  ] 

Q.  Did  they  believe  the  earth  extended  the  same  distance  in  all 
directions  ? 

A.  They  believed  it  to  extend  much  farther  from  east 
to  west  than  from  nortli  to  south. 

[They  observed  that  in  going  east  or  west,  on  the  same  parallel  of  latitude,  no  change  took 
place  in  tlie  appearance  of  the  heavens  ; hut  in  going  north  or  south,  on  the  same  meridian,  every 
sixty  miles  caused  a dift'erence  of  one  degree  in  the  elevation  of  the  pole  and  in  the  position  of  the 
circles  of  daily  motion  of  the  sun  and  other  heavenly  bodies  ; therefore  they  concluded  that  the 
earth  was  very  long  fromrf^ast  to  west,  hut  comparatively  narrow  from  north  to  south  From  this 
originated  the' use  of  the  terms  longitude  and  latitude  ; longitude  meaning  length,  and  latitude, 
breadth  ] 

Q.  What  ideas  had  they  respecting  the  motions  of  the  sun,  moon, 
and  Stai's  ? 

A.  They  supposed  that  they  revolved  around  the 
earth,  from  east  to  west,  every  day. 

Q.  What  was  this  system  called,  that  supposed  the  earth  to  be  at 
rest  in  the  centre,  and  all  the  heavenly  bodies  to  revolve  around  it? 

A.  The  Ptolemaic  system. 

[Ptolemy  asserted,  that  the  sun,  moon,  planet.^  and  stars  revolved  around  the  earth,  from  east  to 
west,  every  ’^4  hours  ; and  to  account  for  their  not  falling  upon  the  earth,  tvhen  they  passed  over 
it.  he  supposed  that  they  were  each  fixed  in  a separate  hollow  crystalline  globe,  one  within  the 
other.  Thus  the  moon  was  in  tlie  first ; Merctjry  in  the  second  ; Venus  in  the  thisd  ; the  sun  in 
the  fourth  ; .Mars  in  the  fifth  ; Jtipiter  in  tlie  sixth  ; Saturn  in  the  seventh  ; — (the  planet  Herschel 
was  not  known  at  this  time) — the  fixed  .stars  in  the  eighth.  He  supposed  the  stars  to  be  in  one 
sphere  as  they  are  kept  in  the  same  positions  with  respect  to  each  other.  To  permit  the  light  of 
the  stars  to  pass  down  to  the  earth,  he  supposed  these  s])heres  or  globes  were  perfectly  clear  or 
transparent  like  gla.ss  The  power  which  moved  these  spheres,  he  supposed,  was  communicated 
from  above  the  sphere  which  contained  the  stars  ] 


LESSON  II. 

Question.  Every  one  is  conscious  that  the  sun,  which  rises  daily  in 
the  east  and  sets  in  the  west,  is  the  same  body  ; where  does  it  go 
during  the  night  ? 

Answer.  It  appears  to  pass  round  under  the  earth. 

Q.  When  we  look  out  upon  the  stars,  on  successive  evenings,  they 
appear  to  have  a definite  position  with  respect  to  each  other,  and  a 
westward  movement  like  the  sun  ; what  motion  do  they  appear  to  have 
from  their  setting  to  their  rising  ? 

A.  They  appear  to  pass  under  the  earth. 

Q.  From  the  north  to  the  south  point  of  the  heavens,  there  is  a con- 
tinuous arc  of  stars,  and  in  their  passage  under  the  earth  they  are  not 
at  all  disarranged,  what  can  you  infer  from  this  fact? 

A.  That  they  pass  completely  around  the  earth,  and 
! every  thing  attached  to  it. 


Q.  We  see  no  body  at  rest  that  does  not  touch  some  permanent  sup- 
port,  hut  we  see  bodies  in  motion  supported  for  different  lengths  of  time, 
without  resting  upon  any  other  surface ; if  the  earth  is  hung  upon 
nothing,  is  it  probably  at  rest? 

A.  It  is  more  probable  that  it  is  in  motion. 

Q.  If  we  throw  a ball,  does  the  same  side  always  remain  forward? 

A.  It  does  not;  it  turns  over  continuously. 

Q.  What  do  we  call  the  line  round  which  it  turns  ? 

A.  Its  axis. 

Q.  If  a fly  were  on  the  ball,  would  distant  objects  appear  to  him  to 
be  stationary? 

A.  They  would  appear  to  revolve  around  the  ball,  as 
often  as  it  turned  over. 

Q.  If  the  earth  is  moving  in  space,  is  it  in  accordance  with  the 
known  motion  of  ordinary  bodies,  to  suppose  that  the  same  side 
remains  forward  ? 

A.  It  is  not.  It  is  more  reasonable  to  suppose  that  it 
turns  on  its  axis. 

Q.  If  the  earth  turns,  and  we  are  carried  round  on  its  surface,  xvhat 
appearance  must  the  sun  and  distant  stars  necessarily  present  ? 

A.  They  must  appear  to  move  around  the  earth  in  the 
opposite  direction. 


LESSON  III. 

Question.  What  other  reason  can  3'ou  give  for  the  earth’s  turning? 

Answer.  The  stars  are  so  distant,  that  their  motion 
would  be  immensely  swift,  in  compari.son  with  the  mo- 
tion of  the  earth,  to  produce  the  same  effect. 

Q.  But  have  we  not  positive  proof,  and  that  too  of  different  kinds, 
that  the  earth  turns  on  its  axis  ? 

yl.  We  have. — 1.  The  shape  of  tlie  earth,  elevated  at 
the  equator  and  depressed  at  the  poles,  can  be  ac- 
counted for  on  no  otlier  supposition. 

2.  A body  at  the  equator,  dropped  from  a great 
height,  falls  eastward  of  the  perpendicular. 

3.  The  trade  winds  and  ocean  currents  in  the  tropi- 
cal regions  are  clearly  traceable  to  the  same  cause. 

Q.  If  the  earth  is  moving  in  space,  does  it  proceed  in  a straight 
line  ? 

A.  It  does  not ; but  it  would  do  so,  Avere  it  not 
attracted  by  other  bodies. 

Q.  What  is  the  attraction,  by  which  all  particles  of  matter  tend 
towards  each  other,  called  ? 

A.  The  attraction  of  gravitation. 

Q.  What  large  body,  by  its  attraction,  causes  the  earth  to  revolve 
around  it  in  a curve  line  ? 

A.  The  sun. 

Q.  What  other  similar  bodies  revolve  around  the  sun  ? 

A.  The  planets. 

Q.  What  may  we  call  the  earth,  when  considered  with  regard  to  its 
size,  shape,  motions,  &c.  ? 

A.  One  of  the  planets. 

Q.  What  science  describes  these  characteristics  of  the  earth,  and 
other  heavenly  bodies  ? 

A.  Astronomy. 


8 


iHERSCMtL 


• ASTP«A 


COMET 


MERCURY# 


VENUS 


EARTH 


MARS 


STEROIDS^!:! 


- COMPARATIVE  MAGNITUDES 

3UPIT£j;^  ' . ' 


I 


I L L U S '1'  11  A 1'  E D 


LESSON  IV. 

ASTRONOMY. 

Question.  What  is  astronomy? 

Answer.  Astronomy  is  tlie  science  wliicli  treats  of  the 
heavenly  bodies. 

Q.  What  arc  the  heavenly  bodies  ? 

A.  The  sun,  moon,  planets,  comets,  and  stars, 

Q.  What  are  some  of  their  characteristics,  of  wiiich  astronomy  treats  ? 
A.  Their  appearance,  size,  shape,  arrangement,  dis- 
tance, motions,  physical  constitution,  mutual  influence 
on  each  other,  &c. 

Q.  Are  they  all  of  the  same  magnitude,  or  size  ? 

A.  The  sun  and  stars  are  much  larger  than  the  other 
bodies. 

Q.  Are  they  all  at  the  same  distance  from  the  earth  ? 

A.  They  are  not ; the  moon  is  the  nearest,  and  the 
stars  the  most  distant. 

Q.  Do  they  all  emit  light  of  themselves? 

A.  They  do  not. 

Q.  How  are  they  divided  in  this  respect? 

A.  They  are  divided  into  two  classes,  luminous  and 
opake. 

Q.  What  is  a luminous  body? 

A.  It  is  a body  which  shines  by  its  own  light. 

Q.  What  is  an  opake  body  ? 

A.  It  is  a .body  which  shines  only  by  reflecting  the 
light  of  a luminous  body. 

Q,  Which  are  the  luminous  bodies  in  the  heavens? 

A.  The  sun  and  fixed  stars  are  luminous  bodies. 

Q.  Which  are  the  opake  bodies  in  the  heavens  ? 

A.  The  moon,  planets,  and  comets. 

Q.  Why  do  the  moon,  planets,  and  comets  appear  luminous? 

A.  Because  they  reflect  to  us  the  light  of  the  sun. 

Q.  What  is  the  shape  of  the  heavenly  bodies  ? 

A.  They  are  round  like  a globe  or  ball. 

Q.  What  do  the  sun,  moon,  planets,  and  comets  constitute  ? 

A.  They  constitute  the  solar  system. 


LESSON  V. 

THE  SOLAR  SYSTEM. 

Question.  How  are  the  bodies  constituting  the  solar  system  arranged  ? 
Answer.  The  sun  is  placed  in  the  centre  of  the  sys- 
tem, with  the  planets  and  comets  revolving  around  it 
at  unequal  distances. 

Q.  How  many  planets  are  there  in  the  solar  system  ? 

A.  Fifty-two  is  the  number  known  at  present. 

Q.  How  are  they  divided  with  respect  to  their  motion  ? 

A.  They  are  divided  into  two  cloisses,  primary  and 
secondary. 

Q.  VV'^hat  is  a [)rimary  planet  ? 

A.  It  is  a planet  which  revolves  around  the  sun  only. 

Q.  What  is  a sticondary  planet  ? 

A.  It  is  a planet  which  revolves  around  its  primary, 
1 and  with  it  around  the  sun. 

Q.  What  are  the  secondary  jdanets  usually  called  ? 

A.  They  are  called  satellites  or  moons. 

Q.  How  many  primary  planets  are  there  ? 

A.  8 large  planets  and  23  asteroids  or  small  planets. 


A S '1'  il  ()  N O MY.  9 


Q.  Wliat  are  their  names,  beginning  at  the  suti  ? 

A.  Mercury,  Venus,  the  Etirth,  Mars,  (Twenty-three 
Asteroids  or  small  Planets,)  .Jupiter,  Saturn,  Herschel, 
or  Uranus,  and  Leverrier,  or  Neptune. 

Q.  How  many  secondary  j)lanets  or  moons  are  there? 

A.  Twenty-one. 

Q.  \Vhich  planets  have  moons  ? 

A.  The  Earth  has  1,  Jupiter  4,  Saturn  8,  Herschel 
6,  and  Leverrier  2. 


LESSON  VI. 

Question.  How  many  revolutions  has  a primary  planet? 

Answer.  Two;  one  on  its  axis,  and  another  around 
the  sun. 

Q.  What  is  the  axis  of  a planet  ? 

A.  It  is  a straight  line,  round  which  it  turns. 

Q.  What  is  the  path  called,  in  which  a planet  revolves  avound  ihe^pn  ? 

A.  It  is  called  its  orltit. 

Q.  What  is  the  earth’s  orbit  ctilled  ? 

A.  It  is  called  the  ecliptic. 

Q.  Why  is  it  so  called  ? 

A.  Because  eclipses  take  place,  only  when  the  moon 
is  in  its  plane.  • 

Q.  How  many  revolutions  has  a secondary  planet? 

A.  T4ree.  1st,  the  revolution  upon  its  axis  ; 2d,  the 
revolution  around  its  primary  ; 3d,  the  revolution  with 
its  primary  around  the  sun. 

Q.  How  are  the  planets  divided,  with  respect  to  their  distance  from 
the  sun  ? 

A.  Into  inferior  and  superior,  according  as  their  dis- 
tance from  the  sun  is  inferior  or  superior  to  that  of  the 
earth. 

qt  Which  arc  the  inferior  planets? 

A.  Mercury  and  Venus. 

Q.  Which  are  the  superior  ? 

A.  Mars,  the  Asteroids,  Jupiter,  Saturn,  Herschel, 
and  Leverrier. 


LESSON  VII. 


DIAMETERS. 

Magnitudfs  ; 
THE  Earth 
BEING  1. 

Distances  from 
THE  Sun. 

Revolution 

O.N 

THEBR  AXIS. 

Revolution 

AROUND 

THE  Sun. 

Miles. 

Miles. 

Days.  Hours. 

Years. 

Days. 

Sun, 

886,952 

1,384,472 

25  10 

Mercury, 

.3,200 

1 

37,000,000 

24 

88 

Venus, 

7,700 

9 

68,000,000 

23J 

224 

Earth, 

7,912 

1 

95,000,000 

24 

1 

0 

Mars, 

4,189 

1 

142,000,000 

24i 

1 

321 

Vesta, 

270 

I 

• • • 'c'STtrh 

22.5,000,000 

Unknown. 

3 

230 

Astriea,  unknown. 

Unknown. 

253,000,000 

(6 

4 

105 

Juno, 

1,400 

254,000,000 

(( 

4 

131 

Ceres, 

1.600 

1 

263,000,000 

44 

4 

222 

Pallas,* 

2,100 

1 

263,000,000 

44 

Hebe,  unknown. 

Unknown. 

Unknown. 

44 

Iris, 

a 

a 

U 

44 

Flora, 

a 

(( 

u 

(4 

Jupiter, 

87,000 

1,280 

485,000,000 

10 

11 

314 

Saturn, 

79,000 

1,000 

890,000,000 

10^ 

29 

167 

Herschel, 

35.000 

80 

1,800,000,000 

84 

5 

Leverrier 

35,000 

80 

2,850,000,000 

166 

* Herschel  estimated  the  diameter  of  each  of  the  asteroids  to  he  under  000  miles.  Their  groat  dis 
tance,  extreme  smallnoss,  and  ucbulous  appearance,  render  it  extremely  difiicult  to  ascertain  their 
size  with  accuracy. 


CIRCLES  NOT  INTHES^PLANE 


AN  OBLIUHEVIEW  OFTKEOUTER  CIRCLE 


APHELION 


MfAN  PLACE 


MEAN  PLACE 


-jjSrmfuc**-  roptf 


CIRCLE 


op  > 


KEPLERS  LAWS 


THE  MEAN  PLACE  OFA 
PLANET  IS  BEFOflETHE  / 
TRUE  PLACE  WHILE  ins/ 
M.0VIN&  FROM  THE  / 
APHELIONTOTHE  /ycl? 
PERIHELION  / . 

d SZ?;f<" 


juNEi”  ® thetrue placeofa  planet 

&'  \ IS  BEfOAETHE  MEANWHILE 

\it1SMOVINC  fROMTHE 
\periheliontothe 

. \ APHELION 

/ ^ JUNE  I”  \ 


J 

I 


ILLUSTRATED 


LESSON  VIII. 

CENTRIPETAL  AND  CENTRIFUGAL  FORCE. 

(^tr.slion.  What  is  tliat  force  called  with  which  all  bodies  attract 
each  other  io  proportion  to  their  mass  ? 

Answer.  The  attraction  of  gravitation. 

Q.  What  is  centripetal  force  ? 

A.  It  is  the  force  vt  hich  draws  a body  towards  the 
centre  round  which  it  is  revolving. 

Q.  What  large  body  by  its  attraction  exerts  a centripetal  force  upon 
all  the  primary  planets  and  comets? 

A.  The  sun. 

Q,  What  body  exerts  a centripetal  force  upon  the  moon  ? 

A.  The  earth. 

Q,  What  bodies  exert  a centripetal  force  upon  the  other  moons  ? 

A.  The  primary  planets  around  which  they  revolve. 

Q.  What  is  the  centrifugal  force  of  a heavenly  body  1 

A.  It  is  that  force  which  moves  it  forward  in  its  orbit, 

Q.  How  do  these  two  forces  cause  the  planets  to  move  ? 

A.  They  cause  them  to  move  in  circular  or  elliptical 
orbits. 

Q.  What  is  a circle  ? 

A.  It  is  a plane  figure  bounded  by  a curve  line,  all  parts 
of  which  are  equally  distant  from  the  centre. — (Fig.  4.) 

Q.  What  is  an  ellipse  ? 

A.  It  is  an  oblique  view  of  a circle.  (Fig.  4.) 

[Note. — Teachers  should  be  sure  that  the  pupils  understand  the  definition  of  an  ellipse,  because 
in  viewing  some  of  the  diagrams  they  may  receive  a wrong  impression.  In  the  diagram  repre* 
seating  the  seasons,  the  earln’s  orbit  appears  very  elliptical : this  would  be  well  understood  by  the 
pupil,  should  the  teacher  call  his  particular  attention  to  it.  Also,  a plane  of  a circle  should  bo  well 
understood.] 

Q.  What  are  the  foci  of  an  ellipse? 

A.  They  are  the  two  points  around  which  the  ellipse 
is  drawn.  (Fig.  7.) 

Q,.  Where  are  these  points  situated  ? 

A.  In  the  greater  axis,  at  equal  distances  from  the 
centre. 

Q.  What  is  the  eccentricity  of  an  ellipse? 

A.  It  is  the  distance  from  the  centre  to  either  of  the 
foci.  (Fig.  7.) 

Q,  Where  is  the  sun  situated  within  the  orbit  of  each  planet? 

A.  It  is  situated  in  one  of  the  foci.  (Fig.  8.) 

Q.  When  are  circles  in  the  same  plane?  (Fig.  b.) 

A.  When  their  planes  lie  in  the  same  straight  line, 

Q.  When  are  circles  not  in  the  same  or  parallel  planes  ? 

A.  When  their  planes  intersect  each  other.  (Fig.  6.) 


LESSON  IX. 

Question.  How  many  laws  did  Kepler  discover,  which  bear  his  name  ? 

Answer.  Three. 

Q.  To  what  do  they  relate  ? 

A.  They  relate  to  the  motions  of  the  planets. 

Q.  What  is  the  first  law  of  Kepler  ? 

A.  That  all  the  planets  revolve  in  elliptical  orbits, 
having  the  sun  in  one  of  their  foci.  (Fig.  7.) 

Q.  What  is  the  second  law  ? 

A.  That  the  radius  vector  passes  over  equal  spaces  in 
equal  portions  of  time. 

Q.  What  is  the  radius  vector  ? 

A.  It  is  a line  drawn  from  the  sun  to  a planet,  in  any 
part  of  its  orbit.  (Fig.  7.) 

Q.  M'hat  is  the  third  law  ? 

A.  It  is  that  the  squares  of  the  times  of  the  revolu- 
tions of  the  planets  around  the  sun,  are  proportional  to 
the  cubes  of  their  mean  distances  from  the  sun. 


ASTRONOMY.  ii 


THE  MEAN  AND  TRUE  PLACE  OP  A PLANET. 

Q.  What  is  the  mean  place  of  the  earth,  or  a planet  in  its  orbit  ? 

A.  It  is  that  point  in  its  orbit  where  it  would  be  if  it 
moved  in  a circle,  and  with  the  same  velocity  at  all 
times.  (Fig.  8.) 

Q.  What  is  the  true  place  of  the  earth  or  a planet  ? 

A.  It  is  that  point  in  its  orbit  where  it  really  is  at  any 
given  time.  (Fig.  8.) 

Q.  What  is  the  aphelion  ? 

A.  It  is  that  point  in  the  orbit  of  the  earth  or  planet 
farthest  from  the  sun.  (Fig.  8.) 

Q.  When  is  the  earth  in  the  aphelion,  or  farthest  from  the  sun  ? 

A.  July  1st.  (Fig.  8.) 

Q.  What  is  the  perihelion  ? 

A.  It  is  that  point  in  the  orbit  of  the  earth  or  planet 
nearest  to  the  sun.  (Fig.  8.) 

Q.  When  isrthe  earth  in  the  perihelion,  or  nearest  to  the  sun  ? 

A.  January  1st.  (Fig.  8.) 

LESSON  X. 

Question.  In  what  points  of  a planet’s  orbit  do  its  mean  and  true 
places  coincide  ? 

Answer.  At  the  aphelion  and  perihelion.  (See  Fig.  8.) 

Q.  What  straight  line  connects  these  points,  and  passes  through  the 
sun  ? 

A.  The  apsis  line. 

Q.  When  is  the  true  place  of  the  earth  or  planet  behind  its  mean 
place  ? 

A.  While  it  is  moving  from  the  aphelion  to  the  peri- 
helion. (See  Fig.  8.) 

Q.  When  is  the  true  place  of  the  earth  or  planet  before  its  mean 
place  ? 

A.  While  it  is  moving  from  the  perihelion  to  the 
aphelion  ? (See  Fig.  8.) 

Q.  When  does  it  move  with  the  least  velocity  ? 

A.  When  it  is  at  its  greatest  distance  from  the  sun. 

Q.  When  is  the  motion  of  the  earth  or  planet  in  its  orbit  increasing? 

A.  When  it  is  moving  from  the  aphelion  to  the  peri- 
helion. 

Q.  Why  does  the  motion  increase  from  the  aphelion  to  the  perihelion  ? 

A.  Because  it  is  approaching  nearer  to  the  sun. 

Q.  What  causes  it  to  approach  the  sun  ? 

A.  The  centrifugal  force  at  the  aphelion  is  not  sufii- 
ciently  great  to  prevent  its  falling  towards  the  sun. 

Q.  When  does  the  earth  or  planet  move  with  the  greatest  velocity? 

A.  When  it  is  the  nearest  to  the  sun. 

Q.  When  is  the  motion  of  the  earth  or  planet  decreasing  ? 

A.  While  it  is  moving  from  the  perihelion  to  the 
aphelion. 

Q.  Why  does  the  motion  decrease  from  the  perihelion  to  the  aphelion  ? 

A.  Because  the  planet  is  receding  from  the  sun. 

Q.  What  causes  it  to  recede  from  the  sun  ? 

A.  The  centrifugal  force  at  the  perihelion  is  so  great 
as  to  carry  it  farther  from  the  sun. 

CENTRIPETAL  AND  CENTRIFUGAL  FORCES. 

A body  projected  by  any  force  would  always  move  forward  in  a straight  line,  and  with  the  same 
velocity,  unless  acted  upon  by  some  other  force.  A ball  discharged  from  a gun  or  thrown  from  the 
hand  soon  looses  its  projectile  force  by  the  resistance  of  the  atmosphere,  and  is  brought  to  the 
ground  by  the  attraction  of  the  earth,  or  centripetal  force.  (Fig.  3 ) These  Iw’O  forces  can  be  well 
Ulustrated,  (Skk  Fig.  I,  2,)  by  tying  a string  to  a ball  and  swinging  it  round  j the  centrifugal  force 
imparted  to  the  ball  by  the  hand  and  by  means  of  the  string,  causes  the  ball  to  move  in  a circle  j but 
if  the  string  should  break,  the  centrifugal  force  would  carry  it  ofl‘  in  a straight  line,  if  the  ball  were 
not  attracted  by  the  earth.  The  string  corresponds  to  the  attraction  of  the  sun  in  our  solar  syg- 
tem,  which  causes  the  planets  to  move  in  regular  curves  around  the  sun,  instead  of  straight  lino. 
If  the  attraction  of  the  sun  or  centripetal  force  should  cease,  the  planets  would  fiy  ofi'  into  space 
in  straight  lines  ; but  if  the  centrifugal  force  should  cease  and  the  centripetal  force  continue,  the 
planets  would  immediately  fail  into  the  sun. 


1 

I 


II 


REMARKABLE  SPOTS  THAT  HAVE 


^ / TM£  tPOrs  KmSTAPP 
/ or  THf  suN.PAst  evtn 


CAP  on  rue  tAtr  HDr\ 
MO  Bictrrejii  on  m itfh 


THCte  SPOTS  eXHItlT  THt  CM  At 
\ uNoeneo  DUA!  ne  T/t£//i  pas 


NOES  WHICH  THErrpeaucHTL  r 
MB  0 VSR  THE  SUM'S  DISK  , 


SOUTH 


TRANSITS  OF  MERCURY  8c  VENUS  UNTIL  THE 


BEEN  DISCOVERED  UPON  THE  SUN 


YEAR  19  00 


:/!*'•** 


NORTH 


LS'JTA 


I L L U S 'I'  11  A 'r  E DAS  T R O X O M Y 


13 


LESSON  XI. 

THE  SUN. 

(^iirs/hn.  What  body  is  in  tlic  centro  of  the  solar  system? 

i AiLswcr.  The  sun. 

(1.  Describe  the  sun  ? 

A.  The  suii  is  a larp^o  luminous  body,  wliich  gives 
' light  and  heat  to  the  whole  solar  system. 

' Q.  What  is  (he  diameter  of  the  sun  ? 

A,  886,952  miles. 

Q.  How  much  larger  is  the  sun  than  the  eartli? 

A.  It  is  1,384,472  times  greater. 

j What  is  the  specific  gravity  oftlie  sun? 

A.  It  is  Is  the  weight  oi' water.  (1.38.) 

Q,  What  is  the  size  of  the  sun  compared  wil'i  the  planets? 

A.  It  is  5U0  tiuies  as  gretil  as  the  bulk  of  all  the 
planets. 

Q.  What  can  you  say  of  its  mass  or  weight  ? 

A.  It  is  about  750  times  the  mass  of  all  the  planets. 

(}.  \\'hat  is  the  distance  of  the  smi  from  the  eartli  ? 

A.  It  is  about  95,000,000  of  miles. 

Q.  What  did  the  ancient  astronomers  consider  the  sun  to  bo  ? 

yl.  A large  globe  of  fire. 

Q,  What  do  astronomers  at  the  present  day  consider  it  to  be  ? 

A.  An  opake  body  like  the  earth,  surrounded  by  a 
luminous  atmosphere. 

Q.  What  motions  has  the  sun  ? 

A.  It  has  three  motions — 1st,  on  its  axis;  2d,  around 
i the  centre  of  gravity  of  the  solar  system;  3d,  around 
j the  centre  of  the  universe. 

[The  term  universe  is  used  by  astronomers,  though  perhaps  improperly,  to  designate  the  great 
cluster  or  firmament  of  stars  in  wliich  our  sun  is  situated.— (Skf,  pao^-s  45  and  46)  This  cluster 
i tic  In  lies  all  ilie  single  stars  th^t  can  be  seen  with  the  naked  eye.  and  all  those  comy>osing  the  galaxy 
or  milky  way  'I'ho  number  of  stars  or  suns  in  the  cluster  is  e.stimatcd  at  many  millions  ; all  which, 
like  our  sun.  are  supposed  to  revolve  around  the  common  centre  of  gravity  of  the  whole  cluster. 
Several  thousand  other  distinct  clusters  or  nebul®,  situated  without  our  firmament,  can  be  seen  by 
the  best  teiescot>es,  nearly  all  of  wliich  are  invisible  to  the  unassisted  eye.] 


LESSON  XII. 

Qupstion.  What  is  the  inclination  of  the  sun’s  axis  to  that  of  the 
ecliptic  ? 

Ansioer.  About  7?  degrees. 

Q.  In  what  time  does  it  revolve  on  its  axis? 

yl.  Ill  about  25  days  and  a half. 

Q.  How  is  the  revolution  of  the  sun  on  its  axis  determined  ? 

yl.  By  spots  on  its  surface,  which  first  appear  on  the 
east  side,  pass  over,  and  disappear  on  the  west  side. 

Q.  What  is  the  nature  of  these  spots  ? 

A.  They  are  supposed  to  be  openings  in  the  luminous 
atmosphere,  which  enable  us  to  see  the  dark  body  of 
the  sun. 

Q.  tVhat  occasions  these  openings  in  the  luminous  atmosphere? 

A.  They  have  been  attributed  to  storms  and  various 
other  causes. 

Q.  Do  these  spots  undergo  any  changes  ? 

yl.  They  are  constantly  changing,  and  sometimes  very 
rapidly.  Some  have  appeared,  others  disappeared  sud- 
denly. 

Q.  On  what  part  of  the  sun  do  they  appear? 

A.  Within  about  thirty  degrees  of  the  equator. 

Q.  Is  the  surface  of  the  sun,  in  the  region  of  the  spots,  tranquil  or 
I agitated  ? 

I yl.  It  is  in  a state  of  continual  and  violent  agitation. 


Q,  W’hat  reasons  have  we  to  suppose  that  the  luminous  part  of  the 
sun  is  intensely  hot? 

A.  1st,  the  heat  of  its  rays,  when  collected  info  a 
focus,  is  very  great.  2d,  its  rays  pass  through  glass 
with  the  greatest  fiicility,  (a  property  belonging  to  arti- 
ficial heat  in  direct  proportion  (o  its  intensity.)  3d,  the 
brightness  of  the  siin  is  grtmter  than  the  most  vivid 
flames,  or  the  most  infensely  ignited  solids, 

LESSON  XIII. 

TRANSIT  OF  MERCURY  AND  VENUS. 

Qitpslion,  WYiat  is  the  transit  of  a heavenly  body  ? 

Ansive?'.  It  is  its  passage  across  the  meridian. 

Q.  What  is  generally  meant  by  the  transit  of  Mercury  and  Venus? 

A.  It  is  (heir  ptissage  across  the  sun’s  disc. 

What  is  the  disc  of  the  sun  or  a planet  ? 

yi.  It  is  the  circular  illuminated  surface  visible  to  us. 

Q.  How  do  Mercury  and  Venus  appear,  when  passing  across  the 
sun’s  disc  ? 

A.  They  appear  like  black  spots  moving  across  the 
sun. 

Q.  What  proof  have  we  that  Mercury  and  Venus  are  not  luminous 
bodies  ? 

A.  When  viewed  with  the  telescope  they  appear 
horned  like  the  moon, 

Q.  On  wliich  side  of  the  sun  does  a transit  begin  ? 

A.  On  the  east  side,  and  terminates  on  the  west  side. 


THB  SPOTS  ON  THE  SUN.  • 

Astronomers  do  not  agree,  in  all  respects,  as  to  the  cause  of  the  spots  on  the  sun  From  the  facts 
already  known,  the  follow’ing  appears  to  be  the  most  rational  view'  ol  the  subject  The  body  of  the 
sun,  wliich  is  opake.  is  surrounded  by  a transparent  atmosphere,  in  which  float  two  strata  of  lumi- 
nous clouds  ; the  lower  stratum  being  more  dense  and  opake.  and  les.s  luminous  than  the  upper; 
wliile  the  latter,  by  its  brilliancy,  furnishes  the  greater  poKion  of  tlie  intense  light  of  the  sun. 
Above  the  upper  stratum,  the  transparent  atmosphere  extends  to  a great  height.  ‘'J'lie  agency  by 
which  the  light  and  heat  of  the  sun  are  generated,  is  not  known.  'l‘he  only  agent  of  which  we 
know,  that  presents  analogous  phenomena,  is  electricity.  The  northern  lights  are  supposed  to 
exhibit,  in  a feeble  manner,  an  action  similar  to  the  luminous  strata  of  the  sun.  The  polar  regions 
of  the  sun  are  tranquil,  and  the  equatorial  comparatively  so  ; but  the  surface  on  each  side  of  the 
equator,  from  16  to  ‘25  degrees  therefrom,  is  in  a state  of  constant  and  violent  agitation  It  is  in  this 
di'^turbed  region  that  the  spots  are  seen  ; no  spot  ever  occurring  farther  tlian  about  30  degrees  from 
the  equator.  The  spots,  besides  revolving  w'ith  the  sun.  are  found  to  have  a motion  from  the  equa- 
tor low'ards  the  poles,  and  when  they  arrive  at  the  comparatively  calm  region,  they  gradually  dis- 
appear. Sometimes  they  close  up  with  great  rapidity,  at  others  they  appear  to  be  suddenly  broken 
into  fragments  and  dispersed  Bright  spots  and  streaks,  called  faculte.  apparently  caused  by  weaves 
in  the  luminous  portion  of  the  atmosphere,  also  appear  on  various  parts  of  the  disc,  but  are  seen 
most  di.stinctly  near  the  margin.  In  the  places  where  spots  appear,  faculte  are  usually  seen  on  the 
day  previous  to  their  breaking  out 

But  w'hat  causes  the  agitation  of  the  sun's  atmosphere,  which  is  so  great  as  frequently  to  burst 
open  the  luminous  strata  ? Astronomers,  at  difl’erent  limes,  have  suggested  various  causes  for  the 
sun’s  spots,  such  as  jets  of  gas  issuing  from  the  sun  and  decomposing  the  luminous  clouds  ; high 
mountains,  extending  through  the  luminous  strata;  volcanoes,  sending  forth  ashes,  smoke,  &c  ; 
to  say  nothing  ol  exploded  theories  of  an  older  date,  such  as  ashes,  scoris,  &c.,  on  the  surface  of 
tlie  melted,  burning  mass  ; or  bodies  very  near  tlie  sun,  revolving  round  it.  But  if  we  are  permit- 
ted to  reason  from  what  takes  place  on  the  earth,  we  would  say,  that  a close  analogy  e.xists 
betw'een  the  phenomena  observed  in  our  owm  atmosphere  and  in  that  of  the  sun.  On  the  earth  the 
heat  of  the  torrid  zone  causes  the  air  to  expand  and  rise,  causing  currents  in  the  lower  part  of  the 
atmosphere  towards  the  equator,  and  in  the  upper  part  of  the  atmosphere  currents  tow'ards  the 
poles.  The  turning  of  the  earth  on  its  axis  causes  the  under  currents  to  take  a westerly  direction, 
while  the  tipper  currents  sweep  in  a curve,  westerly  first,  then  towards  the  poles,  and  finally  east- 
ward. The  principal  disturbance  of  the  atmosphere  caused  by  the  trade  wind  is  in  the  vicinity  of 
the  tropics.  Storms  commencing  in  the  torrid  zone,  are  carried  in  the  direction  of  the  upper  cur- 
rents of  air.  Forinstance,  a storm  started  in  the  West  Indies,  by  the  heating  of  the  air  over  one  of 
its  islands,  thus  causing  an  upward  and  circular  movement  of  the  air.  u.suafly  sweeps  to  the  west 
and  north  over  Florida,  or  the  Gulf  of  Me.xico,  and  then  northeast,  over  the  United  States.  Similar 
causes  acting  upon  the  atmo-sphere  of  tlie  sun.'would  exhibit  phenomena  similar  to  those  which  fli*e 
see.  This  explanation  supposes  the  atmosphere  of  tiie  sun  to  he  warmer  at  the  equator  than  at  the 
poles  ; but  as  the  sun  does  not,  like  the  earth,  receive  its  heat  from  any  extraneous  body,  its  difler- 
ence  of  temperature  must  be  sought  for  in  the  escape  of  its  heat.  It  could  attain  this  condition 
either  by  a more  fiee  radiation  of  heat  at  the  poles  than  at  the  equator,  or  by  its  absorption  as  latent 
heal,  in  the  evaporation  from  large  bodies  of  water  in  the  polar  regions.  As  the  sun  turns  on  its 
axis,  its  equatorial  diameter  must  be  greater  than  its  polar,  and  the  stratum  of  atmosphere  above 
the  luminous  clouds  must  be  thicker  over  the  equatorial  region  than  over  the  polar.  This  must 
render  the  radiation  less  free  at  the  equator  than  at  the  poles,  and  cause  that  part  of  tlie  sun  to  be  of 
a higher  temperature  An  excess  of  heat  at  tlie  sun’s  equator,  with  its  rotation  on  its  axis,  is  sufti- 
cient  to  cause  currents  in  its  atmosphere  similar  to  our  trade  winds,  and  thus  disturb  its  equatorial 
regions  ; and  if  the  spots  are  caused  by  storms  bursting  open  the  luminous  strata,  their  receding 
from  the  equator  towards  the  jioles  is  undoubtedly  the  effect  of  the  same  physical  causes  that  gi\e 
a similar  motion  to  storms  upon  the  earth. 

Some  have  supposed  the  body  of  the  sun  to  be  protected  by  the  lower  opake  portion  of  the  inner 
stratum  of  clouds,  from  the  intense  heat  of  the  luminous  strata,  and  thus  rendered  inhabitable  ; but 
several  objections  will  at  once  arise  to  this  theory.  First,  the  body  of  the  sun  being  surrounded  by 
dense  and  opake  clouds,  could  not  send  off'  Us  heat  into  space  by  radiation,  and  therefore  the  beat 
received  from  tlie  clouds  would  accumulate  and  cause  a high  temperature.  Second,  the  force  of 
gravity  being  about  thirty  times  as  great  as  that  of  the  earth,  a common  sized  man  would  weigh 
some  two  or  three  tons  ; rendering  it  necessary  to  have  an  entirely  different  muscular  organization. 
Third,  it  is  improbable  that  living  beings  would  be  shut  up  within  an  impenetrable  veil,  and  cut  off' 
fiom  a knowledge  of  the  planets,  the  stars,  and  the  countless  w'onders  existing  in  the  boundless 
realms  of  space  These  and  other  considerations  render  it  probable  that  the  sun  is  not  inhabited.  | 


tin:: 


ILLUSTRATED  ASTRONOMY 


15 


Q.  Wliich  sign  does  the  earth  enter  at  tliis  tiiric  ? 

A.  Caj)ricort)iis. 

Q.  Which  signs  does  the  sun  enter,  when  the  north  pole  leans  side- 
ways to  the  sun  '! 


LESSON  XIV. 

ZODIAC. 

Question.  What  is  the  Zodiac? 

Answer.  It  is  a circular  belt  in  the  lieavens  16  degrees 
wide;  8 degrees  on  each  side  of  the  ecliptic. 

Q.  How  is  the  zodiac  divided  ? 

A.  It  is  divided  into  12  equal  parts,  called  signs  or 
constellations  of  the  zodiac. 

Q.  How  is  each  sign  divided  ? 

A.  Each  sign  is  divided  into  30  degrees;  each  degree 
into  60  minutes;  each  minute  into  60  seconds,  ,&c. 

Q.  What  great  circle  is  in  the  middle  of  the  zodiac? 

A.  The  ecliptic,  or  orbit  of  the  earth. 

Q.  What  are  the  names  of  the  constellations  of  the  zodiac  and  the 
signs  of  the  ecli[)tic  ? 

A.  Aries,  Taurus,  Gemini,  Cancer,  Leo,  Virgo,  Libra, 
Scorpio,  Sagittarius,  Capricornus,  Aquarius,  and  Pisces. 

Q.  Do  the  constellations  of  the  zodiac  and  the  signs  of  the  ecliptic 
occupy  the  same  places  in  the  heavens  ? 

A.  They  do  not:  the  signs  in  -the  ecliptic  have  fallen 
back  of  the  constellations  about  31  degrees. 

Q.  Did  the  constellations  of  the  zodiac  and  signs  of  the  ecliptic  ever 
correspond  ? 

A.  They  corresponded  to  each  other  about  22  centu- 
ries ago. 

Q.  What  is  the  cause  of  the  falling  back  of  the  signs  of  the  ecliptic 
among  the  constellations? 

A.  It  is  caused  by  the  retrograde  motion  of  the  equi- 
noxes. (Note.) 

Q.  Upon  what  does  the  length  of  the  seasons  depend  ? 

A.  They  depend  upon  the  revolution  of  the  earth 
from  one  equinox  to  the  same,  again. 

Q.  Does  the  earth  revolve  around  the  sun  in  exactly  the  same  time 
that  it  moves  from  one  equinox  to  the  same  equinox  again  ? 

A.  It  moves  from  either  equinox  to  the  same  again, 
seventeen  minutes  sooner,  than  around  the  sun. 


LESSON  XV. 

Question.  Dons  the  sun  appear  to  move  in  the  heavens  among  the 
sta  I's  ? 

Answer.  It  has  an  apparent  motion  in  the  ecliptic,  east- 
ward around  the  heavens,  during  the  year. 

Q.  How  is  this  appearance  caused,  as  the  sun  is  in  the  centre,  and 
ioes  not  move? 

A.  It  is  caused  by  the  earth’s  moving  around  the  sun. 

Q.  If  the  earth  is  in  the  sign  Aries,  where  does  the  sun  appear  to  be? 

A.  It  appears  to  be  in  the  opposite  sign,  Lihra. 

Q.  As  the  earth  moves  around  in  the  ecliptic,  where  does  the  sun 
appear  to  move  ? * 

A.  It  appears  to  move  in  the  opposite  part  of  the  hea- 
vens, and  in  the  opposite  direction  from  the  motion  of 
the  earth. 

Q.  Which  sign  does  the  sun  enter,  when  the  north  pole  leans  exactly 
towards  the  sun  ? 

A.  Cancer.  (21st  June.) 


A.  Aries  and  Libra. 

Q.  Which  sign  does  the  sun  enter,  when  the  north  pole  leans  exactly 
from  the  sun  ? 

A.  Capricornus.  (22d  December.) 

Q.  Which  are  the  equinoctial  signs? 

A.  Aries,  21st  of  March — Libra,  23d  of  September. 

Q.  Which  are  the  solstitial  signs? 

A.  Cancer,  21st  of  June — Capricornus,  22d  of  De- 
cember. 


LESSON  XVI  . 

Question.  How  are  the  signs  of  the  ecliptic  divided  ? 

Answer.  They  are  divided  into  four  divisions,  corres- 
ponding to  the  seasons. 

Q.  Which  are  the  spring  signs? 

A.  Aries,  Taurus,  Gemini. 

Q.  Which  are  the  summer  signs  ? 

A.  Cancer,  Leo,  Virgo. 

Q.  Which  are  the  autumnal  signs  ? 

A.  Libra,  Scorpio,  Sagittarius. 

Q.  Which  are  the  winter  signs? 

A.  Capricornus,  Aquarius,  Pisces. 

Q.  In  what  time  do  the  equinoxes  fall  back  through  the  whole  circle 
of  the  Zodiac  ? 

A.  25,800  years. 

Q.  What  is  this  time  called? 

A.  The  Platonic,  or  great  year. 

Q.  How  is  this  motion  caused  ? 

A.  It  is  caused  by  a slow  annual  motion  of  the  earth’s 
axis.  (Note.) 

Q.  What  is  longitude  in  the  heavens  ? 

A.  It  is  the  distance  from  the  first  degree  of  the  sign 
Aries,  reckoned  eastward  on  the  ecliptic,  the  whole 
circumference  of  the  heavens. 

Q.  When  the  sun  enters  Aries,  what  is  its  longitude  ? 

A.  It  has  no  longitude. 

Q.  What  is  the  longitude  of  the  earth  at  that  time? 

A.  180  degrees. 

Q.  When  the  sun  enters  Cancer,  what  is  its  longitude  ? 

A.  90  degrees — the  earth’s  longitude  at  the  same 
time  270  degrees. 

Q.  When  the  sun  enters  Libra,  what  is  its  longitude  ? 

A.  180  degrees — the  earth’s  longitude  0 degrees. 

Q.  When  the  sun  enters  Capricornus,  what  is  the  longitude  ? 

A.  270  degrees — the  earth’s  longitude  at  the  same 
time  90  degrees. 

[Note. — This  variation  is  caused  by  the  pole  of  the  earth  varying  a little  every  year  Tins  mo- 
tion of  the  pole  of  the  earth  is  similar  to  that  sometimes  shown  by  a top.  as  it  spins  around  on  the 
point — The  stem  of  the  top  will  have  a circular  motion,  describing  a cone  with  the  ape.x  or  top 
down.  This  circular  motion  of  the  pole  of  the  earth  is  very  slow,  varying  only  50"  every  year, 
and  requires  25,863  years  to  complete  a revolution — which  is  called  the  Platonic  or  great  year. 
The  pole  of  the  earth  is  increasing  its  distance  from  the  north  star  and  in  12,900  years  it  will  be  about 
47®  from  it : and  when  the  north  star  is  on  the  meridian,  it  will  be  in  the  zenith  of  the  noi-thern 
part  of  the  United  States  : but  in  25.800  years  the  pole  will  have  made  a complete  revolution  -so 
that  it  will  point  again  to  the  north  star.] 


I L I.  U S 'r  II  A 1’  K D 


LESSON  XVII. 

MERCURY. 

Queslion.  Which  planet  is  the  smallest  and  nearest  the  sun? 

Answer.  Mercury. 

Q.  What  is  the  diameter  of  Mercury? 

A.  3,200  miles. 

Q.  What  is  its  distance  from  the  sun  ? 

A.  37  millions  of  miles. 

Q.  What  is  its  magnitude,  compared  with  the  earth  ? 

A.  It  is  -n  of  tlie  earth’s  magnitude. 

Q.  What  is  the  specific  gravity  of  the  planet  Mercury? 

A.  It  is  about  15  times  the  weight  ol  water.  (15.111.) 

Q.  In  what  time  does  it  revolve  on  its  axis,  or  perform  its  daily  revo- 
lution ? 

A.  In  about  24  hours.  (24  hours  5 minutes.) 

Q.  In  what  time  does  it  revolve  around  the  sun  ? 

A.  In  about  88  days.  (87d.  23h.  14m.  33s.) 

Q.  How  fast  does  it  move  in  its  orbit  around  the  sun? 

A.  It  moves  112,000  miles  an  hour. 

Q.  What  is  the  light  or  heat  at  Meicury,  compared  with  that  of  the 
earth  ? 

A.  It  is  about  seven  times  as  great. 

Q.  What  is  elongation  ? 

A.  It  is  the  apparent  distance  of  any  planet  from  the 
sun. 

Q.  What  is  the  greatest  elongation  of  Mercury? 

A.  30  degrees;  which  may  be  eitlier  east  or  west  of 
the  sun. 

Q.  Why  is  Mercury  never  seen  in  superior  conjunction  ? 

A.  Because  it  is  so  much  involved  in  the  light  of  the 
sun. 

Q.  Does  Mercury  experience  any  change  of  seasons  ? 

A.  It  does  not,  because  its  axis  is  perpendicular  to  its 
orbit.  This  causes  the  sun  to  be  continually  vertical 
at  the  equator. 


LESSON  XVIII. 

VENUS. 

Question.  What  planet  is  next  to  Mercury? 

Ansiver.  Venus. 

Q.  What  is  the  diameter  of  Venus  ? 

A.  7,100  miles. 

Q.  What  is  its  distance  from  the  sun 
A.  68  millions  of  miles. 

Q.  What  is  its  magnitude  com.pared  with  the  earth  ? 

A.  It  is  about  to  of  the  earth’s  magnitude. 

Q.  What  is  the  specific  gravity  of  Venus  ? 

A.  It  is  5 times  the  weight  of  water.  (5.058.) 

Q.  In  what  time  does  it  revolve  on  its  axis  ? 

A.  In  about  23^  hours.  (23h.  21m.) 

Q.  In  what  time  does  it  revolve  around  the  sun  ? 

A.  In  224  days.  (224d.  16h.  41m.  27s.) 

Q.  How  fast  does  it  move  in  its  orbit  around  the  sun  ? 

A.  It  moves  75,000  miles  an  hour. 

Q.  What  is  the  comparative  light  or  heat  at  Venus  ? 

A.  It  is  about  double  that  of  the  earth. 

Q.  What  is  the  greatest  elongation  of  Venus  ? 

A.  About  47  degrees. 

Q.  When  is  Venus  a morning  star? 

A.  When  it  is  west  of  the  sun,  and  rises  before  it. 

Q.  When  is  it  an  evening  star  ? 

A.  When  it  is  east  of  the  sun,  and  sets  after  it. 


A S T R ()  X O M Y . 17 


Q.  How  long  is  \'emis  a morning  or  an  eiening  star,  alternately? 

A.  About  200  diiys. 

Q.  Why  is  t’eniis  a morning  or  an  evening  star  GO  days  longer  than 
the  time  of  its  revolution  around  the  snn  ? 

A.  Because  the  earth  is  tnoving  around  the  sun  the 
same  way. 

[Sec  diagram.  If  we  sn[)poso  Venus  to  be  in  conjunction,  or  between 
the  earth  and  sun,  as  they  move  the  same  way,  Venus  will  move 
half  around  the  sun,  or  180  degrees,  while  the  earth  moves  only  110 
degrees.  Venus  will  during  this  time  be  a morning  star,  and  when 
Venus  has  completed  its  revolution  around  tin*  sun,  the  earth  will  have 
passed  through  •220  degrees  of  its  Orbit,  and  \Y*iins  will  still  continue  a 
morning  star,  although  it  has  made  a complete  revolution  around  the 
sun.  It  will  therefore  hiive  to  ntidxe  one  complete  revolution  and  lOG 
degrees  over,  before  it  can  be  seen  oti  the  other  side  of  the  sun  ; it  will 
then  be  an  evening  star  for  the  same  length  of  time.] 


LESSON  XIX. 

Question.  How  much  is  the  axis  of  Venus  inclined  to  that  of  its  orbit  ? 

Answer.  75  degrees. 

Q.  When  the  north  pole  of  Venus  inclines  directly  towards  the  sun, 
how  many  degrees  will  the  axis  point  above  the  sun  ? 

A.  Only  15  degrees. 

Q.  How  wide  a torrid  zone  does  this  make  ? 

A.  150  degree.s — 75  degrees  on  each  side  of  tlie 
equator. 

Q.  'I'he  tropics  are  within  how  many  degrees  of  the  poles  ? 

A.  M^ithin  15  degrees. 

t,'.  The  |)olar  circles  are  within  how  many  degrees  of  the  equator  ? 

A.  15  degrees. 

Q.  What  is  the  diameter  of  the  polar  circles  ? 

A.  150  degrees. 

Q.  Has  Venus  any  variation  of  seasons  ? 

A.  She  has  two  summers  and  two  winters  at  the 
equator,  and  a summer  and  winter  at  each  of  the  poles, 
during  the  year. 

Q.  liow  does  Venus  appear  when  viewed  xvith  a telescope  ? 

A.  She  exhibits  phases  similar  to  those  of  the  moon. 

Q.  How  are  conjunctions  divided  ? 

A.  Into  inferior  and  superior. 

Q.  When  is  a planet  in  inferior  conjunction  ? 

A.  When  it  is  between  the  earth  and  sun. 

Q.  What  planets  have  inferior  conjunction  ? 

A.  Mercury  and  Venus;  also  the  moon. 

Q.  When  is  a planet  in  superior  conjunction  ? 

A.  When  it  is  beyond  the  .sun. 

Q.  What  planets  hav*e  superior  conjunction  ? 

A.  All,  except  the  eartli. 

Q.  When  is  a planet  in  opposition  to  the  sun? 

A.  When  it  is  on  the  opposite  side  of  tlie  earth. 

Q.  What  planets  have  opposition  ? 

A.  The  superior  planets. 

Q.  What  apparent  motions  have  the  planets  ? 

A.  Three ; direct,  stationary,  and  retrograde. 

Q.  When  does  a planet’s  motion  appear  to  be  direct  ? 

A.  When  it  appears  to  move  from  west  to  east  among 
the  stars. 

Q.  When  is  a planet’s  motion  said  to  be  stationary  ? 

A.  When  it  is  moving  directly  towards  or  from  the 
earth. 

Q.  When  is  a planet’s  motion  said  to  be  retrograde  ? 

A.  When  it  appears  to  move  backwards,  or  from  east 
to  west  among  the  stars. 


18 


j'€^NORTn^\M  n n ir  a 


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PEHKECI 


ClBClX  or  THE  HEAVEjyj 


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♦ » It.  * * 

* ♦ /C  !!-  « - * 


AF<  DISTANCE  90* 


ILLUSTRATED 


LESSON  XX. 

EARTH,  DEFINITIONS,  &c. 

Question.  Wiiat  is  the  shape  ofthe  eai'th? 

Answer.  It  is  round  like  a globe  or  ball,  a little  flat- 
tened at  the  poles. 

Q.  How  do  we  know  the  earth  to  be  round  ? 

A.  1st.  Navigators  have  sailed  round  it,  by  a con- 
tinued westerly  or  easterly  course. — 2d.  The  top-rnast 
of  a ship  coming  in  from  the  sea,  always  appears  first. — 
3d.  The  earth’s  shadow  upon  the  moon,  in  a lunar 
eclipse,  is  circular. 

Q.  In  what  manner  do  the  inhabitants  stand  upon  the  earth  ? 

A.  They  .stand  with  their  feet  directed  towards  the 
centre  ofthe  earth.  (See  Diagram.) 

Q.  What  do  you  understand  by  the  terms  upward  and  downward  ? 

A.  Upward  is  from  the  centre  ofthe  earth,  downward 
is  towards  the  centre  of  the  earth. 

Q.  What  keeps  the  inhabitants,  (fee.,  upon  the  surface  of  the  earth  ? 

A.  The  attraction  of  tlie  earth. 

Q.  What  is  the  axis  of  the  earth  ? 

A.  It  is  the  .straight  line  round  which  it  performs  its 
daily  revolution. 

Q.  What  are  the  poles  of  the  earth  ? 

A.  They  are  the  extremities  of  its  axis. 

Q.  What  is  the  equator? 

A.  It  is  a great  circle,  whose  plane  divides  the  eartli 
into  northern  and  southern  hemispheres. 

O.  To  what  is  the  plane  ofthe  equator  perpendicular? 

A.  It  is  perpendicular  to  the  earth’s  axis,  and  equi- 
distant from  the  poles. 

Q.  What  is  the  meridian  of  a place  on  the  earth? 

A.  It  is  a great  circle  passing  through  the  place,  and 
the  poles  of  the  earth. 

Into  what  does  the  plane  of  the  meridian  divide  the  earth  ? 

A.  Into  eastern  and  western  hemispheres. 

Q.  What  is  the  latitude  of  a place  on  the  earth  ? 

A.  It  is  its  distance  from  the  equator,  north  or  south. 

Q.  On  what  is  it  measured  ? 

A.  On  a meridian  ? 

Q.  How  far  is  latitude  reckoned  ? 

T..  Ninety  degrees  ? 

Q.  What  places  have  90  degrees  of  latitude  7 

A.  The  poles. 


LESSON  XXI. 

Q.  Which  is  the  first  meridian  ? 

A.  It  is  the  meridian  from  which  longitude  is  reck- 
oned, 

Q.  Which  meridian  is  generally  used  in  this  country  as  the  first 
mej  idian  ? 

A.  The  meridian  of  London, 

Q.  WTat  is  the  longitude  of  a place  on  the  earth  ? 

A.  It  is  its  distance  east  or  west  of  the  first  meridian. 

Q.  What  angle  expresses  the  longitude  of  a place? 

A.  The  angle  between  the  meridian  of  the  place,  and 
the  first  meridian. 

Q.  Where  is  this  angle  f<)rmed  ? 

A.  At  the  poles,  where  the  meridians  intersect  each 
other. 

Q.  On  what  circle  is  this  angle  measured  ? 

A.  On  the  equator. 


A S T R O N O MY.  19  j j 

Q.  How  far  is  terrestrial  longitude  reckoned  ? 

A.  It  is  reckoned  180  degrees,  or  half  round  the  earth. 

Q.  What  is  the  horizon  ? 

A.  It  is  a great  circle  which  separates  the  visible 
heavens  from  the  invisible, 

Q.  How  many  horizons  are  there  ? 

A.  Two;  the  visible  and  the  rational. 

Q.  MTat  is  the  visible  or  sensible  horizon  ? 

A.  It  is  that  circle  where  the  earth  and  sky  appear 
to  meet. 

Q.  What  is  the  rational  horizon  ? 

A.  It  is  a great  circle,  parallel  to  the  visible  horizon, 
w hose  plane  passes  through  the  centre  of  the  earth. 

Q.  Into  what  does  it  divide  the  earth  ? 

A.  Into  upper  and  lower  hemispheres. 

Q.  Is  the  rational  horizon  above  or  below  the  visible  horizon  ? 

A.  It  is  below  the  visible  horizon. 


LESSON  XXII. 

Q.  Do  all  places  on  the  earth  have  the  same  horizon  ? 

A.  They  do  not;  if  w^e  change  our  place  on  the  earth, 
the  horizon  changes. 

Q.  What  are  the  poles  of  the  horizon  ? 

A.  The  zenith  and  nadir. 

Q.  What  is  the  zenith  ? 

A.  It  is  that  point  in  the  heavens  directly  over  oui 
heads, 

Q.  Do  all  places  have  the  same  zenith  ? 

A.  They  do  not ; every  place  has  a different  zenith. 

Q,  What  is  the  nadir  ? 

A.  It  is  that  point  in  the  heavens  which  is  opposite  to 
the  zenith,  or  directly  under  our  feet. 

Q.  Are  the  zenith  and  nadir  fixed  points  in  the  heavens  ? 

.A.  They  are  not;  they  make  a complete  revolution 
in  the  heavens  every  24  hours. 

Q.  What  is  the  altitude  of  a heavenly  botly  ? 

A.  It  is  its  height  or  distance  from  the  horizon. 

Q.  What  is  the  altitude  of  the  star  at  A ? (See  Diagram.) 

A.  It  has  no  altitude,  being  in  the  liorizon, 

Q.  What  is  the  altitude  of  the  star  at  B ? also  at  C ? (See  Diagram.) 

Q.  What  is  the  polar  distance  of  a heavenly  body? 

A.  It  is  its  distance  from  the  pole. 

Q.  What  is  the  polar  distance  of  the  star  at  D ? also  at  E.  and  F ? 
(See  Diagram.) 

Q.  Who  are  the  antipodes? 

A.  Those  wdio  live  on  directly  opposite  sides  of  the 
earth. 

Q.  Who  are  the  antceci  ? 

A.  Those  w'ho  live  in  equal  latitude,  on  directly  oppo- 
site sides  of  the  equator. 

Q.  Who  are  the  perioeci  ? 

A.  Those  who  live  in  equal  latitude  on  opposite  sides 
of  the  pole. 

Q.  What  ppc\iliarity  of  circumstances  have  the  antipodes? 

A.  They  have  opposite  latitude,  seasons,  longitude, 
and  day  and  night. 

Q.  What  have  the  antceci  ? 

A.  They  have  opposite  latitude  and  seasons,  but  the 
same  longitude,  and  day  and  night. 

Q.  What  have  the  perioeci  ? 

A.  They  have  the  same  latitude  and  seasons,  but 
opposite  longitude,  and  day  and  night. 


90 


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SMORTIST  C/VVS  t LONCLST  N &HTS 


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I L L U S T R A TED  A S 'I'  R ()  N O ]\I  Y . 


21 


LESSON  XXIII. 
EARTH  AND  SEASONS. 


Question.  What  is  the  shape  of  the  earth? 

Answer.  It  is  round  like  a globe  or  ball,  a little  Ibit- 
tened  at  the  poles 

Q,  What  is  its  position  in  the  solar  system  ? 

A.  It  is  the  third  planet  from  the  sun. 

Q.  What  is  the  mean  diameter  of  the  earth  ? 

^.7,912  miles.  [Equatorial  diameter  7,926  miles; 
polar  diameter  7,899  miles.) 

Q.  How  much  greater  is  the  equatorial  than  the  polar  diameter  ? 

A.  About  27  miles. 

Q.  What  causes  the  equatorial  diameter  to  he  greater  than  the  polar? 

A.  It  is  caused  by  the  revolution  of  the  earth  on  its 
axis. 

[As  the  greater  portion  of  the  surface  of  Uie  earth  is  covered  with 
water  ; and  as  the  earth  revolves  on  its  axi^he  water  recedes  from 
the  poles  towards  the  equator,  until  its  tendency  to  run  back  towards 
the  poles,  just  balances  the  effects  of  the  centrifugal  force.  This 
causes  the  equatorial  diameter  to  be  greater  than  the  polar.  If  the 
earth  should  stop  revolving  on  its  axis,  the  water  at  the  equator  would 
settle  away  towards  the  poles,  until  the  earth  had  assumed  the  form  of 
a globe  as  near  as  possible.  Thus  large  portions  of  land  in  the  torrid 
zone,  which  are  now  covered  by  the  ocean,  would  be  left  dry,  and  new 
continents  and  islands  would  be  formed.] 

Q.  What  is  the  mean  distance  of  the  earth  from  the  sun  ? 

2.  About  95,000,000  of  miles. 

[The  mean  distance  of  a j)lanet,  is  the  distance  it  would  always  bo 
from  the  sun,  if  its  orbit  should  be  reduced  to  a true  circle.] 

Q.  What  is  the  specific  gravity  of  the  earth? 

A.  It  is  52  times  the  weight  of  water.  (5.48.) 

Q.  In  what  time  does  the  earth  revolve  on  its  axis,  or  perform  its 
diurnal  revolution  ? 

A.  In  24  hours.  (In  23  hours  56  minutes ; as  seen 
from  the  stars.) 

Q.  Which  way  does  it  revolve  ? 

A.  From  west  to  east. 

Q.  What  causes  day  and  night  ? 

A.  The  light  of  the  sun  causes  day,  and  the  shade 
of  the  earth  causes  night. 

Q.  How  great  a portion  of  the  earth  is  continually  in  the  light  of  the 
sun  ? 

A.  One  half;  the  other  half  being  in  the  shade  of  the 
earth. 

Q.  What  does  the  revolution  of  the  earth  upon  its  axis,  cause  ? 

A.  The  succession  of  day  and  night. 


LESSON  XXIV. 

Question.  As  the  earth  turns  upon  its  axis,  what  effect  is  produced  ? 

Answer.  The  sun  is  continually  rising  to  places  in  the 
west, -and  continually  setting  to  places  in  the  east. 

Q.  In  what  time  does  the  earth  revolve  around  the  sun,  or  perform 
its  annual  revolution  ? 

A.  In  365  days  6 hours. 

Q.  How  fast  does  it  move  in  its  orbit  around  the  sun? 

A.  68,000  miles  an  hour. 

Q.  How  are  the  changes  of  the  seasons  caused  ? 

A.  They  are  caused  by  the  earth’s  axis  being  inclined 
to  that  of  its  orbit,  and  its  revolution  around  the  sun. 


Q.  How  many  degrees  is  the  earth’s  axis  inclined  towards  its 
orbit  ? 

A.  Twenty-three  degrees  atid  a half  (23"  28'.) 

Q.  Is  the  direction  of  the  earth’s  axis  changed  during  the  year  ? 

A.  Its  chatige  is  so  slight  that  it  may  be  considered 
as  pointing  to  the  same  place  in  the  heavens. 

Q.  When  does  the  north  pole  lean  directly  towards  the  sun? 

A.  On  the  21st  of  June,  called  the  summer  solstice. 
(See  Diagram.) 

Q.  How  many  degrees  does  it  lean  towards  the  sun  ? 

A.  23i  degrees  ; and  the  sun  is  vertical  23.2  degrees 
north  of  the  equator. 

Q.  What  seasons  docs  this  produce  ? 

A.  Summer  in  the  northern  hemisphere,  and  winter 
in  the  southern. 

Q.  When  does  the  north  pole  lean  directly  fi-om  the  sun  ? 

A.  On  the  22d  of  December,  called  the  winter  sol- 
stice. (See  Diagram.) 

Q.  When  the  north  pole  leans  from  the  sun,  what  are  the  sea- 
sons ? 

A.  Winter  in  the  northern  hemisphere,  and  summer 
in  the  southern. 


LESSON  XXV. 

Question.  At  what  points  of  the  ecliptic  is  the  earth  at  the  time  of 
the  solstices  ? 

A.  At  the  solstitial  points. 

Q.  Through  how  much  of  its  orbit  does  the  earth  pass,  in  moving 
from  one  solstitial  point  to  the  other? 

A.  One  half  of  its  orbit,  or  from  one  side  of  the  sun  to 
the  other. 

Q.  What  are  those  two  points  called  half  way  between  the  solstitial 
points  ? 

A.  The  equinoctial  points.  (See  Diagram.) 

Q.  Why  are  they  so  called  ? 

A.  Because,  when  the  earth  is  in  these  points,  the 
sun  is  vertical  at  the  equator,  and  the  days  and  nights 
are  every  where  equal. 

Q.  When  is  the  sun  at  the  vernal  equinox  ? 

A.  On  the  21st  of  March. 

Q.  When  is  it  at  the  autumnal  equinox  ? 

A.  On  the  23d  of  September. 

Q.  Which  way  does  the  pole  lean  when  the  earth  is  at  the  eqinoc- 
tial  points  ? 

A.  It  leans  sideways  to  the  sun,  the  sun  being  verti- 
cal at  the  equator. 

Q.  When  the  north  pole  leans  towards  the  sun,  why  is  summer  pro- 
duced in  the  northern  hemisphere  ? 

A.  Because  the  rays  of  the  sun  strike  it  so  directly  as 
to  cause  many  rays  to  fall  on  a given  surface. 

Q.  When  the  north  pole  leans  from  the  spn,  why  is  winter  produced 
in  the  northern  hemisphere  ? 

A.  Because  the  rays  of  the  sun  strike  it  so  obliquely, 
that  they  spread  over  a greater  surface. 

Q.  At  what  points  do  the  ecliptic  and  equinoctial  intersect  each 
other  ? 

A.  At  the  equinoctial  points.  (See  Diagram.) 

Q.  How  far  are  the  solstitial  points  from  the  equinoctial  points  ? 

A.  Ninety  degrees. 


tt 


I T.  L U S T R A T E D A S T R ()  N O M Y . 


/wO 


AEROLITES,  METEORS,  &c. 

1 Question.  What  are  meteors  ? 

Answer.  They  are  luminous  bodies  seen  in  the  ni^lit 
shooting  through  the  heavens. 

Q.  What  are  they  usually  called? 

A.  Shooting  stars,  and  sometimes  fire-balls. 

Q.  What  is  an  aerolite  ? 

A.  It  is  a stone  falling  from  the  air. 

Q.  Have  stones  ever  been  known  to  fall  from  the  air? 

A.  They  have,  and  in  great  numbers.  (See  Table.) 

Q.  How  did  Laplace,  Olbers,  and  other  astronomers  account  for 
the  falling  of  these  stones? 

A.  They  believed  that  they  were  ejected  from  vol- 
canos in  the  moon,  beyond  the  moon’s  attraction,  and 
therefore  attracted  to  the  earth. 

Q.  How  did  they  account  for  the  meteors  ? 

A.  They  believed  them  to  be  gaseous  matter  col- 
lected in  the  upper  regions,  and  ignited  by  some  un- 
known cause. 

Q.  What  is  the  present  tlieory  in  regard  to  aerolites  and  meteors  ? 

A.  Astronomers  believe  that  they  have  the  same 
origin. 

Q.  Do  all  meteors  produce  stones  which  fall  to  the  earth  ? 

A.  They  do  not;  very  few  of  them  are  of  suffi- 
cient density  to  reach  the  earth  before  they  are 
consumed. 


Q.  Do  tliese  meteors  originate  in  our  atmosphere  ? 

A.  The  most  of  them  have  their  origin  far  beyond 
our  atmosphere. 


Q.  What  is  the  present  theory  of  meteors? 

A.  Astronomers  maintain  that  the  planetary  regions 
contain  detached  portions  of  chaotic  and  uncon- 
densed matter,  and  that  the  earth  in  its  orbit  fre- 
quently meets  with  such  masses. 


Q.  What  effect  would  be  produced  by  such  contact? 

A.  The  matter  in  its  passage  through  the  atmos- 
phere would  suddenly  be  ignited  and  the  gaseous 
portion  consumed,  and  the  mineral  portion,  if  any, 
would  be  condensed  and  precipitated  to  the  earth  in 
the  form  of  a stone. 


Q.  What  is  a peculiar  characteristic  of  meteoric  stonSs? 

A.  They  are  composed  of  the  same  materials  an;! 
nearly  in  the  same  proportions,  and  are  unlike  any 
combination  of  minerals  found  on  the  earth. 

Q.  What  does  this  fact  prove  ? 

A.  It  conclusively  proves  that  they  have  a common 
origin. 


Q.  When  was  the  greatest  meteoric  dfsplay  ever  known  ? (See 
Note  2.) 

A.  On  the  night  of  the  12th  and  13th  of  No^a^iiber, 
1833. 


Q.  What  was  the  altitude  of  the  meleors  on  this  occasi? 

A.  Prt/essor  Olmstead  says  they  were  not  less  than 
2238  miles  above  the  earth. 


Suh.^tance. 

Place. 

Period. 

Shower  of  stones 

.At  Korno 

Under  Tullus  Hostiliu.s. 

Shower  of  stones 

At  Homo 

Consuls  C.  iMarlius  and  Tor- 

quatiis. 

Shower  of  iron 

In  Lucania 

Year  before  the  defeat  of 
Crassus. 

Shower  of  mercury 

[n  Italy 

Large  stone 

Near  the  river  Negos,  Thrace 

Second  year  of  the  70lt»  Olym- 

Year  before  J.  C.  45‘i. 

Three  large  stoites 

In  Thrace 

Shower  of  fire 

.At  Qnesnoy 

January  4^1717. 

Stone  ol  7i2  ihs. 

Near  Larissa,  Macedonia 

January,  1706. 

About  l iOO  Slones — one  of  1-20  } 
lbs  , another  of  60  lbs.  ^ 

Near  Padua.  Italy 

Ill  UlO. 

Another  of  51)  lbs. 

On  Mount  Vasier,  Province 

November  27,  1037. 

Sliower  of  Sand  for  15  hours 

In  the  Atlantic 

April  6,  1719. 

Shower  of  sul[)hur 

Sodom  ami  (lomorra 

Sulphurous  luin 

In  the  Duchy  of  Mansfield 

In  1658. 

The  same 

Copenhagen 

Ill  tots. 

Shower  of  sulphur 

Brunswick 

October,  1721. 

Shower  of  unknown  matter 

Ireland 

In  1695. 

Two  large  stones,  weighing  ? 
SiO  lbs.  $ 

Liponas,  in  Bresse 

September,  1753. 

stony  mass 

.Niort,  Normandy 

In  1760. 

A stone  of  7 1*2  lbs. 

At  Luce,  in  Le  Maine 

September  13,  17GS 

.A  stone 

.\t  Aire,  in  Artois 

In  176.S. 

A stone 

In  Le  Cotenlin 

In  1768. 

Extensive  .shower  of  stones 

Environs  of  Agen 

Inly  ’j;,  1790. 

About  iZ  stones 

Sienna,  Tnscanv 

July,  1791. 

A l^rge  stone  of  56  lbs. 

Wold  Cottage,  Yorkshire 

December  13,  1795. 

A stone  of  about  20  lbs. 

Sale,  Department  of  the  Rhone 

.March  17,  1768. 

A stone  of  10  lbs. 

in  Portugal 

February  19.  1796. 

Show'er  of  stones 

Benares,  East  Indies 

December  19,  1793 

Shower  of  stones 

At  Plana,  near  Tabor,  Bohemia 

Jnlv  3,  170.'}. 

Mass  of  iron,  70  cubic  feet 

America 

-April  6.  ISOO 

Mass  of  iron,  14  quintals 

.•\bakauk,  Siberia 

Very  old. 

Shower  of  stones 

Rarboiitan,  near  Roquefort 

.Inly,  1789. 

Large  stone  of  260  lbs. 

Ensisheim,  Upper  Rhine 

November  7,  1492. 

Two  stones,  200  and  300  lbs. 

Near  Verona 

In  1767. 

March  12,  1793 

A stone  of  20  lbs. 

Sales,  near  Ville'Franclie 

Several  stones  from  10  to  17  } 
lbs.  ^ 

.Near  LhAigle,  Normandy 

1 

April  26,  1803, 

NOTE. 


One  of  the  instances  in  the  table  is  of  sufficient  interest  to  deserve  a notice. 

A singular  relation  respecting  the  stone  of  Knsisheini  on  the  Rhine,  (at  which 
philosophy  once  smiled  incredulously,  regarding  it  as  one  of  the  romances  of  the 
tiiiddle  ages,)  may  now  be  admitted  to  sober  attention  as  a piece  of  authentic  history. 

A homely  narrative  of  its  fall  was  drawn  up  at  the  time  by  order  of  the  emperor  Max- 
imilian, and  depo.sited  with  the  stone  in  the  church.  It  may  thus  be  rendered  ; — “In 
the  year  of  the  Lord  14.‘)2,  on  Wednesday,  which  was  Martinmas  eve,  the  7th  of 
November,  a singular  miracle  occurred  ; for,  between  eleven  o’clock  and  noon,  there 
was  a loud  clap  of  thunder,  and  a prolonged  confused  noise,  which  was  heard  at  n 
great  distance  ; and  a stone  fell  from  the  air,  in  the  jurisdiction  of  Ensisheim,  which 
weighed  two  hundred  and  sixtv  pounds,  and  the  confused  noise  was.  besides,  much 
louder  than  here.  Then  a child  saw  it  strike  on  a field  in  the  upper  jurisdiction, 
towards  the  Rhine  and  Inn,  near  the  district  of  Giscano,  which  was  sown  with  wheat, 
and  it  did  it  no  harm,  except  that  it  made  a hole  there  ; and  then  they  conveyed  it  from 
that  spot ; and  many  pieces  were  broken  from  it,  whicb  the  landvogt  forbade.  They, 
therefore,  caused  it  to  be  placed  in  the  church,  with  the  intention  of  suspending  it  as  a 
miracle : and  there  came  here  many  people  to  see  this  stone.  So  there  were  remarka- 
able  conversations  about  this  stone : but  the  learned  said  that  they  knew  not  what  it 
was  ^or  it  was  beyond  the  ordinary  course  of  nature  that  such  a large  stone  should 
smite  the  earth  from  the  height  of  the  air  ; but  that  it  was  really  a miracle  of  God  ; for,  | 
before  that  time,  never  anything  was  heard  like  it,  nor  seen,  nor  described.  When 
they  found  that  stone,  it  had  entered  into  the  earth  to  the  depth  of  a man’s  stature, 
which  every  body  explained  to  be  the  will  of  God  that  it  .should  be  found;  and  the 
noise  of  it  was  heard  at  Lucerne,  at  Viiting,  and  in  many  other  places,  so  loud  that  it 
was  believed  that  houses  had  been  overturned:  and  as  the  King  .Maximilian  was  here 
the  Monday  after  St.  Catharine’s  day  of  the  same  year,  his  royal  Excellency  ordered 
the  stone  which  had  fallen  to  be  brought  to  the  Castle,  and,  after  having  conversed  a 
long  time  about  it  with  the  noblemen,  he  said  that  the  people  of  Ensisheim  should  take 
it,  and  order  it  to  be  hung  up  in  the  church,  and  not  to  allow  any  body  to  take  anything 
from  it.  His  Excellency,  however,  took  two  pieces  of  it ; of  which  he  kept  one,  and 
sent  the  other  to  the  Duke  .■'igi.-mund  of  Austria  : anil  they  spoke  a great  deal  about 
thi.s  stone,  which  they  suspended  in  the  choir,  where  it  still  is  ; and  a great  many  peo- 
ple came  to  see  it.”  Contemporary  writers  confirm  the  substance  of  this  narration, 
and  the  evidence  of  the  fict  exists  ; this  aerolite  is  precisely  identical  in  its  chemical 
composition  with  that  of  other  meteoric  stones.  It  remained  for  three  centuries  sus- 
pended in  the  church,  was  carried  off  to  Colmar  during  the  French  revolution  ; but 
has  since  been  restored  to  its  former  site,  and  Ensisbeim  rejoices  in  the  possession  of 
the  relic. 

NOTES. 

We  now  come  to  by  far  the  most  splendid  display  on  record  ; and  as  it  was  the  third 
in  successive  years,  and  on  the  same  day  of  the  month,  it  S'^eiped  to  invest  the 
meteoric  showers  with  a periodical  character;  and  hence  originated  the  title  of 
November  meleors.  An  incessent  play  of  dazzlingly  brilliant  meleors  was  kept  up  in 
the  heavens  for  several  hours  Some  of  these  were  of  considerable  magnilnde  and 
peculiar  form.  One  of  large  size  remained  for  some  time  almo.ct  stationary  in  ibe  zenith, 
over  the  Falls  of  Niagara,  emitting  streams  of  light.  The  wild  dash  of  the  waters,  as 
contrasted  with  the  fiery  uproar  above  ibem,  formed  a scene  of  unequalled  sublimity. 

In  many  districts,  tbe  mass  of  the  population  were  terror-struck,  and  tbe  more  enlight- 
ened were  awed  at  conterniilaling  so  vivid  a picture  of  the  Apocalyptic  image — that  of 
the  stars  of  heaven  f.dling  to  the  earth,  even  as  a fig-tree  casting  her  untimely  figs,  when 
she  is  shaken  of  a mighty  wind.  A planter  of  South  Carolina  thus  describes  the  efl'ect 
of  the  scene  upon  the  ignorant  blacks; — I was  suddenly  awakened  by  the  most  dis- 
tres.sing  cries  that  ever  fell  on  my  ears.  Shrieks  of  horror  and  cries  for  mercy  I could 
hear  from  most  of  the  negroes  of  three  qilantations,  amounting  in  all  to  about  six  or 
eight  hundred.  While  earnestly  listening  for  the  cause,  1 heard  a faint  voice  near  the 
door  calling  my  name.  I arose,  and  taking  my  sword,  stood  at  the  door.  .At  this 
moment.  T heard  the  same  voice  still  beseeching  me  to  ri.«e,  and  saying  ‘ O mj' Cod. 
the  world  is  on  fire.’  1 then  opened  the  door,  and  it  is  difficult  to  say  which  excited 
me  rno.-^t — tbe  avvfiilness  of  the  scene,  or  the  distressed  cries  of  the  negroes.  Upwards  | 
of  one  hundred  lay  prostrate  on  the  ground — some  speechless,  and  some  with  the  bit-  j 
terest  cries,  but  with  their  hands  ri'.rsed,  imploring  God  to  save  the  world  and  them. 
The  scene  was  truly  awful  ; for  never  did  rain  fill  much  thicker  than  the  meteors  fell  1 
towards  the  earth;  east,  west,  north  and  south,  it  vvas  the  same.”  I 


Wl 


I L L U S T II  A T i:  D AS  T R O N 0 M Y . 25 


LESSON  XXVI. 
MARS. 


Question.  What  is  Mars  ? 

Answer.  Mars  is  the  fourth  planet  from  the  sun. 

Q.  What  can  you  say  of  its  size  ? 

A.  It  is  the  smallest  except  Mercury  and  the  asteroids. 

Q.  What  is  its  diameter  ? 

A.  4,189  miles. 

Q.  What  is  its  distance  from  the  sun  ? 

A.  142  millions  of  miles. 

.Q.  What  is  its  magnitude  ? 

A.  It  is  about  one  seventh  of  the  size  of  the  earth. 

Q.  What  is  the  specific  gravity  of  Mars  ? 

A.  It  is  about  five  times  the  weight  of  water.  (5.19.) 

Q.  In  what  time  does  it  revolve  on  its  axis  ? 

A.  In  about  242  hours.  (24h.  39m.  22s.) 

Q.  In  what  time  does  it  revolve  around  the  sun  ? 

A.  In  one  year,  321  days. 

Q.  H o\v  fast  does  it  move  in  its  orbit  ? 

A.  55,000  miles  an  hour. 

Q.  How  many  degrees  does  the  axis  of  Mars  lean  towards  its  orbit? 

A.  About  30  degrees,  (30®  18'.)  (See  Diagram.) 

Q.  Does  Mars  have  any  change  of  seasons  ? 

A.  The  seasons  are  similar  to  those  of  the  earth,  but 
nearly  twice  as  long. 

Q.  Why  are  they  longer  ? 

A.  Because  Mars  is  nearly  two  of  our  years  in  revolv- 
ing around  the  sun. 

Q.  What  is  the  appearance  of  Mars  when  seen  with  the  naked  eye? 

A.  It  appears  of  a red,  fiery  color. 


LESSON  XXVII. 

Q.  H ow  does  Mars  ajipear  when  viewed  with  a telescope  ? 

A.  Outlines  of  apparent  continents  and  seas,  are  dis- 
tinctly seen. 

Q.  What  appearance  have  the  continents  ? 

A.  They  have  a ruddy  color,  arising  probably  from 
the  nature  of  the  soil. 

Q.  Of  what  color  are  the  seas  ? 

A.. They  appear  of  a greenish  color,  caused  no  doubt 
by  contrast  with  the  red  color  of  the  continents. 

Q.  Does  Mars  present  different  phases  ? 

A.  It  sometimes  appears  gibbous. 

Q.  When  does  a planet  appear  gibbous  ? 

A.  When  we  can  see  more  than  half,  but  not  the 
whole,  of  the  illuminated  surface. 

Q.  Does  Mars  ever  appear  horned  like  the  moon  ? 

A.  It  does  not,  because  it  does  not  pass  between  us 
and  the  sun. 

Q.  What  other  appearances  does  Mars  exhibit  -when  viewed  with  a 
telescope  ? 

A.  Bright  spots  are  seen  alternately  at  the  poles. 

Q.  When  do  these  spots  appear  ? 

A.  When  it  is  winter,  or  continual  night  at  the  poles. 

Q.  What  is  supposed  to  be  the  cause  of  these  spots  ? 

A.  Snow  and  ice,  which  has  accumulated  at  the  poles 
during  u inter. 


Q.  Do  these  spots  continue  through  the  year  ? 

A,  They  entirely  disappear  as  the  summer  advances 
upon  the  poles. 

Q.  What  amount  of  light  and  heat  has  Mars  ? 

A.  It  has  about  half  as  much  as  the  earth. 


ASTEROIDS. 

Question.  What  are  the  asteroids  ? 

Answer.  They  are  small  bodies  between  the  orbits 
of  Mars  and  Jupiter. 

Q.  How  many  are  there'? 

A.  Twenty  three  is  the  number  known  at  present. 

Q.  What  is  their  magnitude  ? 

A.  They  are  very  small  with  the  exception  of  Pallas. 

Q.  What  have  some  astronomers  supposed  in  regai  d to  them  ? 

A.  That  they  were  once  united  in  one  planet ; but 
blown  to  pieces  by  some  internal  explosion. 

Q.  What  facts  do  they  advance  to  prove  this  theory  ? 

A.  They  are  rough  with  sharp  angular  points. 


NOTE. 

Astronomers  in  comparing  the  distances  of  the  planets,  found  that  there  was  a 
great  distance  between  Mars  and  Jupiter  which  did  not  coincide  with  the  unifor- 
mity exhibited  by  the  other  planets.  This  led  them  to  suspect  that  there  was  an 
undiscovered  planet  circulating  in  that  region,  and  Baron  de  Zach  went  so  far  as 
to  calculate  in  1784-5,  the  orbit  of  this  ideal  planet.  So  confident  were  astrono- 
mers of  the  existence  of  a planet,  that  in  1800,  six  astronomers,  of  whom  Baron 
de  Zach  was  one,  assembled  at  Lilienthal,  and  formed  an  association  of  twenty- 
four  observers,  the  principal  object  of  which  was  to  use  their  own  language  “ to 
force  this  planet  from  the  regions  of  analogy  into  the  realms  of  sense  ; ” but  before 
they  had  got  fully  organized.  Piazza  discovered  Ceres ; after  another  year  Olbers 
discovered  Pallas,  and  Juno  and  Vesta  were  brought  in  at  intervals  of  a few  years. 
The  search  continued  fruitless  for  ten  years,  it  was  fairly  concluded  that  this  region 
was  exhausted.  In  consequence  of  the  discovery  of  four  small  planets  instead 
of  one  large  planet,  the  new  and  somewhat  novel  idea  was  advanced  by  Dr.  Olbers, 
that  these  bodies  were  originally  united  in  one  planet;  but  by  some  internal  ex- 
plosion had  been  blown  in  pieces. 

This  theory  has  been  fully  discussed  by  astronomers  from  that  time  to  the  pres- 
ent day.  Several  support  the  theory  of  Olbers,  while  others  discard  it  entirely 
as  untenable.  In  1845,  astronomers  turned  their  telescopes  again  to  this  field  for 
exploration,  and  they  have  succeeded  in  discovering  Jimeteen  new  asteroids  which 
makes  the  whole  number  twenty-three.  The  first  tour,  Ceres,  Pallas,  Juno  and 
Vesta  are  from  the  sixth  to  the  eighth  magnitude ; while  the  nineteen  new  o.nes 
are  less  than  the  ninth  in  magnitude ; all  of  these  bodies  are  very  small  and  are 
rough  with  sharp  angular  points  ; these  facts  would  seem  to  indicate  that  they  had 
formerly  been  united  in  one  body. 

The  following  is  a list  of  the  names,  date  of  discovery,  and  by  whom  discovered. 


Name  and  Number. 

Date  of  Discovery. 

Name  of  Discoverer. 

1.  Ceres 

1800,  Jan.  1. 

Piazza,  of  Sicily. 

2.  Pallas 

1802,  Mar.  28. 

Olbers,  of  Bremen. 

3.  Juno 

1804,  Sept.  1. 

Harding. 

4.  Vesta 

1807,  Mar.  29. 

Olbers. 

5.  Astrea 

1845,  Dec.  8.  , 

Hencke,  of  Germany. 

6.  Hebe 

1847,  July  1. 

Hencke. 

7.  Iris 

1847,  Aug.  13. 

Hind,  of  London. 

8.  Flora 

1847,  Oct.  18. 

Hind. 

9.  Metis 

1848,  April  26. 

Graham,  of  Ireland. 

10.  Hygeia 

1849,  April  12. 

De  Gasparis,  of  Naples. 

11.  Parthenope 

1850,  May  11. 

De  Gasparis. 

12.  Victoria 

1850,  Sep.  13. 

Hind. 

13.  Egeria 

18.50,  Nov.  2. 

De  Gasparis. 

14.  Irene 

1851,  May  19. 

Hind. 

15.  Eunomia 

1851,  July  29. 

De  Gasparis. 

16.  Psyche 

1852,  Mar.  17. 

De  Gasparis. 

17.  TheMs 

18.52,  April  17. 

Luther,  of  Germany. 

IS.  Melpomene 

1852,  June  24. 

Hind. 

19.  Fortuna 

18.52,  Aug.  22. 

Hind. 

20.  Massilia 

18.52,  Sept.  19, 

De  Gasparis. 

21.  Lutetia 

18.52,  Nov.  15. 

Goldschmidt,  of  Germany. 

22.  Calliope 

1852,  Nov.  16. 

Hind. 

23.  Thalia. 

18.52,  Dec.  1.5. 

Hind.  1 

26 


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ILLUSTRATED  A S T R O N O M Y . 27 


LESSON  XXVIII. 

JUPITER. 

Question:  What  is  Jupiter  ? 

Answer.  Jupiter  is  the  largest  planet  in  the  solar 
system. 

Q.  How  many  times  larger  is  Jupiter  than  the  earth? 

A.  It  is  1,280  times  greater. 

Q.  What  is  the  specific  gravity  of  Jupiter? 

A.  It  is  about  H times  the  weight  of  water.  (1.30.) 

Q.  How  far  is  Jupiter  from  the  sun? 

A.  485  millious  of  miles. 

Q.  What  is  its  diameter  ? 

A.  87,000  miles. 

Q.  Which  diameter  is  the  greater,  the  polar  or  equatorial  ? 

A.  The  equatorial  diameter  is  6,000  miles  greater 
than  the  polar. 

Q.  What  causes  the  equatorial  diameter,  so  much  to  exceed  the  polar  ? 

A.  The  quick  rotation  of  the  planet  upon  its  axis. 

Q.  In  what  time  does  it  revolve  upon  its  axis  ? 

A.  In  about  10  hours.  (9h.  55m.  50s.) 

Q.  In  what  time  does  it  revolve  around  the  sun  ? 

A.  In  eleven  years,  314  days. 

Q.  How  fast  does  it  move  in  its  orbit  around  the  sun  ? 

A.  30,000  miles  an  hour. 

Q.  How  many  moons  has  Jupiter  ? 

A.  Four. 

Q.  What  is  their  magnitude  ? 

A.  They  are  about  the  size  of  our  Moon. 

Q.  Who  first  discovered  them  ? 

A.  Galileo,  the  inventor  of  the  telescope  in  1610. 

Q.  How  are  the  orbits  of  these  Moons  situated  ? 

A.  They  are  directly  over  his  equator. 

Q.  Do  these  moons  frequently  eclipse  the  Sun  ? 

A.  They  do  at  each  revolution  around  the  Sun. 

Q,  What  great  discovery  was  made  by  observing  these  eclipses  ? 

A.  The  velocity  of  Light.  (Note.) 

Q-  Has  .Jupiter  any  change  of  seasons? 

A.  It  has  no  change  of  seasons. 

Q.  Why  do  its  seasons  not  change  ? 

A.  Because  its  axis  is  nearly  perpendicular  to  the 
plane  of  its  orbit,  Avhich  causes  the  sun  to  be  always 
vertical  at  the  equator.  (See  Diagram.) 

Q.  H ow  does  Jupiter  a|)pear,  when  viewed  with  a telescope  ? 

A.  Light  and  dark  belts  appear  to  surround  it.  (See 
Fig.  1 and  2.) 

Q.  What  are  the  light  belts  ? 

I A.  They  are  supposed  to  be  clouds,  which  are  thrown 
' into  parallel  lines  by  the  quick  rotation  of  the  planet 
upon  its  axis. 

Q.  What  are  the  dark  belts  ? 

A.  They  are  probably  the  body  of  the  planet,  seen 
between  the  clouds. 

Q.  Do  these  belts  always  appear  the  same  ? 

A.  They  change  frequently,  and  sometimes  the 
clouds  break  to  pieces.  (See  Fig.  3.) 

Q.  What  is  the  velocity  of  its  equatorial  parts,  in  turning  on  its  axis  ? 

A.  25,000  miles  an  hour. 

Q.  What  amount  of  light  and  heat  has  Jupiter  ? 

A.  It  has  27  times  less  than  the  earth. 


SATURN’S  RINGS. 

{From  the  JJmerican  Jllmanac  and  liepository  of  useful  Knowledge,  1852). 

Wn  M T a few  months  the  inquiry  has  been  started  with  fresh  interest,  By  how  many  rings  is 
Saturn  siinoundcd,  and  in  what  way  are  these  rings  sustained  ? Short  saw  two  or  three  divisions 
outside  ol  the  centre  of  breadth.  Herschcl  the  lirst,  in  1780,  saw  a new  division  near  the  innet 
, edge.  As  tliis  appearance  was  temporary,  he  thought  that  observation  would  not  justify  the  sup- 
po.sition  of  multiple  rings.  Lines  of  demarcation  were  seen  on  both  rings  in  1813  and  1814.  Que> 
telet  saw  the  outer  ring  divided  m 18*23  In  1825  and  18*26  three  divisions  were  seen  on  the  outer 
ring  by  Kater.  In  1H37  Encke  noticed  that  the  outer  ring  was  divi  led,  and  that  there  were  se- 
veral marks  near  the  inner  edge  of  the  inner  ring.  De  Vico  has  given  an  account  of  several  divi- 
sions seen  by  him  on  both  rings.  In  1838  several  divisions  were  seen  at  Home,  which  arc  described 
by  Decuppis.  In  1643,  Lassell  and  Dawes  saw  a division  of  tlie  outer  ring.  Smyth  gives  an  ac- 
count of  the  last  case,  and  adds  : “After  such  unquestionable  evidence,  there  can  be  no  reason- 
able doubt  of  the  outer  ring’s  being  multiple  ” On  the  1 1th  of  November,  IS.7O,  G.  P.  Bond  saw 
what  he  thouglit  at  the  time  a second  division  of  the  ring,  near  tlic  inner  edge  of  the  inner  ring. 
On  the  15th,  his  father  thought  the  new. ring  was  wholly  disconnected  with  the  old,  though  the 
edge  next  to  the  planet  w'as  Ijetter  defined  than  the  outer  edge.  Micrometric  observations  gave 
for  the  inner  diameter  of  the  inner  division  26“. 3,  whereas,  according  to  Kncke,  the  inner  diameter 
of  the  old  inner  ring  should  be  at  that  time  29“ 8.  From  this  it  was  inferred  that  the  large  re- 
fractor at  Cambridge  had  revealed  an  entirely  unknow'n  and  darker  ring  of  Saturn,  which  was  not 
to  be  confounded  with  the  division  of  the  old  inner  ring  which  had  frequently  been  noticed.  The 
outer  edge  of  the  new  ring  Is  l“.d  within  the  inner  edge  of  any  ring  hitherto  visible.  This  con- 
clusion was  confirmed  by  observations  continued  for  several  w’eeks.  Similar  appearances  were 
noticed  on  the  ‘25th  and  26th  ol  November,  by  Mr.  Dawes,  and  afterwards  by  Lassell  of  Liverpool, 
and  Schmidt  of  Bonn. 

On  the  16th  of  April,  1861,  G P.  Bond  communicated  to  the  American  Academy  of  Arts  and 
Sciences  at  Boston,  a memoir  on  the  rings  of  Saturn.  Alter  rehearsing  the  facts  already  detailed 
in  regard  to  extraordinary  divisions  of  the  rings,  he  draws  attention  to  the  circumstance  that  other 
observers,  as  Struve,  Bessel,  J,  F.  W.  Ilerschel,  and,  we  may  add,  Smyth,  have  seen  only  the  usual 
division,  even  with  the  best  instruments,  and  under  the  most  favorable  circumstance.?.  More- 
over, the  divisions  on  both  rings  are  not  always  seen  simultaneously  ; and  the  Cambridge  teles- 
cope w'hich  has  brought  to  view  a ring  always  before  invisible,  does  not  indicate  any  of  the  un- 
usual divisions  in  the  two  ol<l  rings.  It  seems  a Justifiable  conclusion  from  all  the  facts,  that  the 
multiplicity  of  rings  occasionally  seen,  and  the  failure  to  discern  more  than  two  at  other  times, 
are  not  referrable  to  the  diflcrencc  of  instruments,  to  the  greater  or  less  purity  of  tlie  air,  or  to 
the  unequal  skill  of  observers,  but  to  a material  fluctuation  in  the  ring  itself. 

In  a lecture  publicly  delivered  in  Reading,  Pennsylvania,  on  the  3d  of  January,  18.51,  Mr. 
Kiikwood  made  the  following  remarks  : — “ This  gives  rise  to  the  interesting  question  whetherthe 
rings  of  Saturn  may  not  be  the  most  recent  cosmical  formation  within  the  limits  of  the  solar  sys- 
tem, and  whether  it  may  not,  in  the  course  of  future  ages,  collect  about  a nucleus  and  constitute  a 
satellite.  The  evidence  of  its  solidity  is  not,  I think,  by  any  means  conclusive.  On  the  other 
hand,  observations  made  within  the  last  few  years  give  a degree  of  plausibility  to  the  presumption 
that  it  may  he  in  a state  of  fluidity.  I refer  to  the  occasional  appearance  of  dark  lines,  chiefly  on 
the  outer  rings,  which  have  been  supposed  to  indicate  a subdivision  into  several  concentric  an- 
nuli. They  do  not,  however,  appear  to  be  permanent ; at  least  they  are  subject  to  some  change, 
as  they  are  not  always  visible  even  when  circumstances  would  seem  most  favorable. 

Such  are  the  considerations  which  led  Mr.-Bond  to  reject  the  idea  of  solid  rings,  and  to  sup- 
pose these  appendages  of  Saturn  to  be  fluid  or  semi  fluid.  If  tliis  is  the  material,  it  is  unnecessary 
to  suppose  that  the  inner  and  outer  stirfaces  move  round  in  the  same  time.  The  velocity  at  every 
point  may  be  such,  that  the  centrifugal  and  other  forces  balance  each  other.  “ And  even  should 
an  accumulation  of  disturbances,  of  which  the  absence  of  inequalities  lessens  the  probability, 
bring  the  rings  together,  the  velocities  at  the  point  of  contact  will  be  very  nearly  equal,  and  the 
two  will  coalesce  without  disastrous  consequences.”  “ If.  in  its  normal  condition,  the  ring  has  but 
one  division,  as  is  commonly  seen,  under  peculiar  circumstances  it  might  be  anticipated  that  the 
preservation  of  their  e(|uilihrium  would  require  a separation  in  some  regions  of  either  tlie  inner 
or  outer  ring;  this  would  explain  the  fact  of  occasional  subdivisions  being  seen.  There-being 
visible  but  for  a short  time,  and  then  disappearing  to  the  most  powerful  telescopes,  is  accounted 
for  by  the  removal  of  the  sources  of  disturbance,  when  the  parts  thrown  ofl'  would  reunite  ” 

“ Finally,  a fluid  ring,  symmetrical  in  its  dimensions,  is  not  of  necessity  in  a state  of  unstable 
equilibrium,  with  reference  either  to  Saturn  or  the  other  rings.” 

At  the  meeting  at  Cincinnati  of  the  American  Association  for  the  Advancement  of  Science, 
Professor  B.  Peirce,  read  a memoir  on  the  constitution  of  Saturn's  ring,  containing  the  same 
general  views  which  he  submitted  to  the  American  Academy  of  Arts  and  Sciences  at  Boston,  on 
the  I5th  of  .‘^pril,  1851.  Mr.  Peirce  arrives  at  the  same  results  by  analysis  as  those  which  Mr. 
Bond  had  derived  from  observations,  illustrated  and  combined  by  bis  own  ingenious  compulations. 
Mr  Peirce  differs  in  opinion  from  Laplace,  in  regard  to  the  efficacy  of  an  irregular  figure  in  sus- 
taining  Saturn's  ring.  He  considers  this  statement  of  Laplace,  which  his  successors  have  blindly 
adopted,  as  a careless  suggestion,  and  not  the  ripened  fruit  of  his  usual  rigid  examination.  “ I 
maintain.”  he  says,  “ unconditionally,  that  there  is  no  conceivable  form  of  hTegulanly,  consistent 
with  an  actual  ring,  which  would  serve  to  retain  if  permanently  about  the  prhnai'y,  if  it  ivere  solid."'^ 

Tlie  stability  of  the  ring  does  not  depend  on  the  attraction  exerted  on  it  by  the  planet. 
In  the  circulation  of  the  fluid  annulus  around  Saturn,  the  velocity  is  least  at  the  greatest  dis- 
tance.  Hence  the  matter  accumulates  at  the  most  remote  point  of  the  ring,  and  to  such  an  extent 
that  the  quantity  of  matter  balances  the  distance,  and  the  attraction  exerted  by  the  ring  and  the 
planet  on  each  other  is  the  same  in  every  direction.  The  ring  is  held  together  l)y  the  attraction 
of  the  primary  ; but  it  is  not  sustained  as  a whole  by  the  primary.  It  is  sustained  by  the  satellites. 
The  satellites  disturb  it,  and  sustain  it  by  a delicate  equipoise  of  disturbances.  Something  like 
this  restorative  action  had  been  hinted  at  by  Sir  J.  F.  W Herschel.  But  the  remedial  power  is  insuf- 
ficient to  sustain  a solid  ring.  It  follows  that  no  planet  can  have  a ring  unless  richly  provided 
with  menials  to  hold  it.  Saturn  alone  of  all  the  planets  seems  competent  to  preserve  a ring  when 
once  bestowed. 

Mr.  Peirce  concludes  his  memoir  with  the  following  weighty  paragraph  : “Were  the  ring, 
however,  supposed  to  he  a large  gaseous  mass  of  a circular  figure,  the  condensation  which  would 
occur  at  the  point  of  aphelion  might  easily  lead  to  chemical  action.  Precipitation  might  ensue, 
and  the  necessary  consequence  would  seem  to  be  a continually  accelerated  accumulation  at  this 

fioint,  which  would  terminate  in  the  formation  of  a planet.  Under  this  modification,  the  nebular 
lypothesis  may  possibly  be  free  from  some  of  the  objections  with  which  it  has  been  justly  as- 
sailed. But  in  approaching  the  forbidden  limits  of  human  knowledge,  it  is  becoming  to  tread  with 
caution  and  circumspection.  Man’s  speculations  should  be  subdued  from  all  rashness  and  extrav 
agance  in  the  immediate  presence  of  the  Creator. 

[The  rings  of  Saturn  have  been  considered  by  the  most  celebrated  astronomers.  Laplace,  Struve, 
Bessel,  Sir  William  Herschel,  J.  F.  W.  Herschel,  Smyth  and  others,  as  being  solid  bodies  surround- 
ing the  planet  and  of  the  same  materials  and  density  ; but  Mr.  G.  P.  Bond  of  Cambridge,  and  Pro- 
fessor Pierce,  have  advanced  a new  theory  in  regard  to  these  rings,  that  they  are  a fluid  or  semi- 
Liquid  matter.  In  regard  to  this  novel  Theory  it  is  not  considered  by  astronomers  as  fully  estab- 
lished. We  have  not  adopted  this  new  theory  in  this  work,  preferring  to  wait  for  a further  de- 
monstration of  it.  We  are  however  inclined  to  believe  that  the  various  phenomena  are  more 
easily  explained  upon  this  hypothesis. — Author. 


NOTE. 

In  1675  it  was  observed  by  Roemer  a Danish  Astronomer,  that  when  the  earth  was  nearest  to 
Jupiter  the  eclipses  of  his  sattellites  took  place  8 minutes  13  seconds  sooner  than  the  time  specified 
in  the  astronomical  tables  ; but  when  the  earth  was  farthest  from  Jupiter,  the  eclipses  took  place 
8 minutes  13  seconds  too  late,  the  difference  being  16m.  26s.  From  this  it  appears  that  it  takes  light 
16m.  26s.  to  pass  across  the  earth’s  orbit  which  is  190  millons  of  miles  in  diameter— 190  millions  of 
miles  divided  by  986  the  number  of  seconds  in  16m-  26s.  gives  192,697  miles  as  the  velocity  of  light 
per  second. 


28 


VIEW  OP 


SATUFIV^ 

C , -^. 


0 MOONS  AS  SEENFROMTHE  PLANE  V AT  MIDNICrIT 
^,0F;THE  PLAKET  upon  TH£  HINCj' 


I L L U S T R A T E D A S T R O N O M Y . 


LESSON  XXIX. 

SATURN. 

• Qv'xtion.  WiiAT  is  Saturn  ? 

ybisive)'.  It  is  the  largest  planet  except  Jupiter. 

Q.  Wliat  is  its  magnitude  comparefi  with  the  earth  ? 

A.  It  is  about  1,000  times  larger. 

Q.  What  is  its  specific  gravity  ? 

A.  It  is  about  one  half  the  weight  of  water.  (0.56.) 

Q,  What  is  the  diameter  of  Saturn  ? 

A.  79,000  miles. 

Q.  What  is  its  distance  from  the  sun  ? 

A.  890  millions  of  miles. 

Q.  In  what  time  does  it  revolve  on  its  axis  ? 

A.  In  about  IO2  hours.  (lOh.  29m.  16s.) 

Q.  In  what  time  does  it  i-evolve  around  the  sun  ? 

A.  In  29  years  and  a half  (29y.  167d.) 

Q.  IIow  fast  does  it  move  in  its  orbit  around  the  sun? 

A.  22,000  miles  an  hour. 

Q.  Is  there  any  change  of  seasons  at  Saturn? 

A.  There  is,  but  it  is  very  slow,  as  it  takes  nearly 
thirty  of  our  years,  to  complete  a year  at  Saturn. 

Q.  How  much  does  the  axis  of  Saturn  lean  towards  its  orbit? 

A.  About  30  degrees.  (28°  40'.)  (See  Diagram.) 

Q,  How  long  is  it  day  and  night  alternately  at  the  poles  ? 

A.  About  15  of  our  years.  (See  Diagram.) 

Q.  What  has  Saturn  which  surrounds  it? 

A.  Two  large  rings  of  solid  matter  like  the  planet. 
(See  Diagram.) 

Q.  What  is  theii  position  around  the  planet  ? 

A.  They  are  directly  over  the  equator. 


LESSON  XXX. 

Q,  Do  these  rings  revolve  with  the  planet ! 

A.  They  do,  and  in  nearly  the  same  time  as  the 
planet. 

Q.  Are  these  rings  connected  with  the  planet  or  separate  ? 

A.  They  are  separate  from  the  planet  and  from  each 
other. 

Q.  Whai  is  the  distance  from  the  planet  to  the  inner  ring  ? 

A.  19,000  miles. 

Q.  How  wide  is  tlie  inner  ring? 

A.  17,000  miles. 

Q. , How  wide  is  the  space  between  the  rings  ? 

A.  About  1,800  miles. 

Q.  What  is  the  width  of  the  outer  ring? 

A.  10,000  miles. 

Q.  How  thick  are  these  rings  ? 

A:  About  100  miles.  (Some  say  1,000  miles.) 

Q.  Are  these  rings  uniform  ? 

A.  They  are  rough  and  uneven. 

Q,  How  many  satellites  or  moons  has  Saturn  ? 

A.  Eight. 

Q.  What  is  the  position  of  their  orljits  ? 

A.  Their  orbits,  excepting  one,  are  directly  over  the 
rings.  (See  Diagram.) 


2!)  1 

I 

Q.  Does  the  sun  always  shine  on  tlie  same  side  of  the  rings  ? j 

A.  It  shines  upon  each  side  alternately  for  lifteen  i 
years.  (See  Diagram.) 

Q.  What  amount  of  liglit  and  heat  has  Saturn  ? 

A.  It  has  90  times  less  than  the  earth. 

Q.  What  appearance  has  the  disc  of  Saturn  ! 

A.  It  has  dark  belts  similar  to  those  of  Jupiter. 


Saturn. 

According  to  heathen  mythology,  Saturn  was  the  deity  who  pre- 
sided over  time.  He  is  sometimes  represented  as  an  old  man,  flying 
with  wings  attached  to  his  back  ; carrying  an  hour-giass  in  one  hand, 
and  a scythe  in  the  other.  These  are  very  appropriate  emblems  of 
time  ; the  old  man  represents  titne,  his  flying  admonishes  us  to  improve 
every  moment  as  it  comes,  or  it  will  be  lost ; the  hour-glass  reminds 
us  that  our  life,  like  the  sand  in  the  glass,  will  soon  run  out ; and  the 
scythe,  like  time, 

“ Cuts  down  fill, 

Both  great  and  small.” 

Saturn  is  the  6th  lunar  planet  from  the  sun,  and  the  most  remarka- 
ble ; it  is  next  in  order  to  Jupiter,  and  the  most  remote  planet  from  the 
earth,  of  any  that  are  visible  to  the  naked  eye.  It  may  easily  be  dis- 
tinguished from  the  fixed  stars  by  its  pale,  feeble  and  steady  light.  It 
is  890  millions  of  miles  from  the  sun,  and  revolves  around  it  in  29 
years  167  days ; so  that  its  apparent  motion  among  the  stars  is  very 
slow,  being  only  12  degrees  in  a year.  Saturn,  besides  being  attended 
with  seven  moons,  is  surrounded  by  two  large  concentric  rings,  which 
are  separate  from  each  other,  and  also  from  the  planet.  The  matter, 
of  which  these  rings  are  composed,  is  undoubledl}'  no  less  solid  than 
the  planet,  and  they  are  observed  to  cast  a strong  shadow  upon  the 
planet  itself.  Saturn,  in  bulk,  is  about  1,000  times  larger  than  the 
earth,  and  revolves  on  its  axis  in  lOh.  29m.  16s.  This  rapid  motion 
upon  its  axis,  causes  it  to  be,  like  Jupiter,  very  much  flattened  at  the 
poles.  So  that  the  equatorial  diameter  is  to  the  polar,  as  12  to  11. 
The  rings  of  Saturn  present  a phenomenon,  to  which  there  is  nothing 
analagous  in  the  rest  of  the  solar  system.  These  rings  are  very  thin, 
one  wdthin  the  other,  and  directly  over  the  equator.  They  revolve 
round  in  the  same  time  with  the  planet,  although  they  are  detached 
from  it. 

The  axis  of  Saturn  is  inclined  to  that  of  it’s  orbit  28°  40',  and  as 
the  rings  are  in  the  plane  of  the  equator,  the  axis  of  the  rings  has  the 
same  inclination.  It  will  be  seen  fj'om  this,  (see  Diagram,)  that  the 
sun  shines  alternately  for  15  years  on  one  side  of  the  rings,  and  then 
upon  the  other  ; so  that  if  we  lived  upon  the  rings,  we  should  have 
continued  day  for  15  years,  and  then  continual  night  for  the  same  length 
of  time. 

The  I’ings  of  Saturn  must  present  to  the  inhabitants  of  the  planet  a 
most  magnificent  spectacle.  They  apjrear  like  vast  arches,  or  semi- 
circles of  light,  extending  from  the  eastern  to  the  western  horizon.  At 
the  equator,  the  outer  ring  is  not  visible,  being  hidden  from  the  view 
by  the  inner  ring ; but,  in  about  45  degrees  of  latitude,  both  rings  are 
visible,  and  present  a magnificent  appearance.  During  the  day-time, 
they  appear  dim  like  a white  cloud,  but,  as  the  sun  goes  down  their 
brightness  increases ; while  the  shadow  of  the  planet  is  seen  to  come 
on  at  the  eastern  limb  of  the  ring,  and  gradually  rise  to  the  zenith, 
(see  Diagram,)  when  it  passes  down  and  disappears  in  the  M’estern 
horizon  at  the  rising  of  the  sun.  The  rays  of  the  sun  always  fall  upon 
the  side.s  of  the  rings  very  obliquely,  as  the  sun  is  never  seen  more  than 
30  degrees  above  the  horizon  of  the  rings,  while  at  other  times  the 
edge  of  the  rings  only  is  presented  to  the  sun.  (See  Diagram.)  These 
rings  are  rough  and  of  unequal  width  and  thickness,  and  it  has  been 
demonstrated  that  these  rings  could  not  maintain  their  stability  of  rota- 
tion, if  they  were  in  all  parts  of  equal  thickness  and  density,  as  the 
smallest  disturbance  would  destroy  their  equilibrium,  which  would  con- 
tinue to  increase  until  at  last,  they  would  be  precipitated  upon  the  planet. 

Saturn  has  seven  moons,  or  satellites,  but  they  are  only  seen  with  a 
good  telescope.  Their  orbits,  with  the  exception  of  the  seventh,  are 
nearly  m the  plane  of  the  rings  ; the  seventh,  which  is  the  farthest 
from  the  planet,  is  the  largest,  and  its  orbit  is  considerably  inclined  to  the 
plane  of  the  rings.  (See  Diagram.) 


K‘»»i 

11^2121 

ILLUSTRATED  A S 1'  R O N O M Y . 


.‘II 


LEVERRIER,  OR  NEPTUNE.— Continued. 


LESSON  XXXI. 

HERSCHEL,  OR  URANUS. 

Question.  WuKN  was  Ilerscliel  or  Uranus  discovered  ? 

Ansiuer.  in  1781. 

Q.  F»y  wliom  ? 

A.  Cy  Sir  William  Ilerschel,  v.  ho  was  a celebrated 
English  astronomer. 

In  wliat  part  of  the  solar  system  is  Ilerse.hel  situated? 

A.  It  is  theTtli  hirge  planet  from  the  sun,  and  next  to 
the  farthest  discovered. 

Q.  What  is  its  rnagnitiule? 

A.  It  is  80  times  larger  than  the  earth. 

Q.  What  is  its  sj)ecific  gravity  ? 

A.  It  is  I 2 times  the  weiglit  of  water.  (1.53.) 

Q.  What  is  its  distance  from  the  sun  ^ 

A.  1800  millions  of  miles. 

Q.  In  what  time  does  it  revolve  on  its  axis? 

A.  It  is  not  certainly  known,  [it  has  been  stated  at 
1 ilay  18  hours,  but  there  seems  to  be  no  proof  of  it.] 
Professor  Nichol. 

Q.  In  xx'hat  time  does  it  rexmlve  around  the  sun  ? 

A.  In  about  84  years.  (84y.  6t/.) 

Q.  How  fast  does  it  mox'e  in  its  orbit  around  the  sun  ? 

A.  15,000  miles  an  hour. 

Q.  How  will  the  light  and  heat  at  Herschel,  compare  with  the  same 
at  the  earth  ? 

A.  They  are  368  times  less. 

Q.  How  many  moons  has  Herschel  ? 

A.  Six  moons  were  seen  by  Sir  Wm.  Herschel,  but 
only  three  have  been  seen  by  other  astronomers. 

Q.  What  angle  do  the  orbits,  of  the  two  whieh  are  best  knoxvn, 
make  with  the  ecliptic? 

A.  An  angle  of  78  degrees.  (78°  58'.) 

Q.  In  what  direction  do  these  moons  move  in  their  orbits  ? 

A.  They  move  from  east  to  west,  contrary  to  the  mo- 
tions of  all  the  other  planets,  both  primary  and 
secondary. 

LESSON  XXXII. 

I.SVERRIER,  OR  NEPTUTTE. 

. Q.  Whkn  was  Neptune  discovered  ? 

A.  In  1846,  by  Dr.  Galle,  of  Berlin. 

Q.  Who  published  the  elements  of  this  planet,  and  directed  astrono- 
mers to  the  point  in  the  heavens  wh(>re  it  might  be  discovered  ? 

A.  Leverrier,  a celebrated  French  mathematician. 

Q.  How  near  the  point,  xvhere  he  directed  astronomers  to  look,  was 
it  found  ? 

A.  Within  one  degree. 

Q.  What  is  the  diameter  of  this  planet? 

A.  It  is  aUout  35,000  miles. 

Q.  What  is  its  magnitude  ? 

A.  It  is  about  80  times  larger  than  the  earth. 

Q.  What  is  its  distance  from  the  sun  ? 

A.  About*2,850  millions  of  miles. 

Q.  In  what  time  does  it  revolve  on  its  axis  ? 

A.  It  is  not  known. 


Q.  In  what  lime  does  it  revolve  around  the  sun  ? 

yl.  In  about  166  years. 

Q.  How  many  moons  has  Lex’erricr  ? 

A.  One ; and  another  is  sujtposed  to  have  been  seen. 

Q.  What  amount  of  light  and  heat  has  this  planet  ? 

A.  About  000  times  less  than  that  of  the  earth. 

(J.  Does  this  ])lanet  correspond  to  the  calctdations  of  Leverrier,  as  to 
mass  and  distance  from  the  sun  ? 

A.  Its  mass  and  distance  are  considerably  less  than 
his  calculations. 

Q,  What  have  these  circumstances  led  some  astronomers  to  suppose  ? 

A.  That  Leverrier  is  one  of  a group  of  planets  similar 
to  the  Asteroids,  situated  at  nearly  the  same  distance 
from  the  sun. 

Q.  Are  the  primary  planets  inhabited? 

A.  They  appear  to  be  inhabitable. 

[Note. — The  presence  of  clouds  indicating  both  air  and  water  ; the 
regular  succession  of  the  seasons,  as  well  as  day  and  night ; the  suita- 
ble amount  of  light  received  from  the  sun  ; the  accompaniment  of 
moons  ; the  specitic  gravity  of  bodies  at  their  surface  ; all  seem  to 
indicate  that  the  primary  planets  are  suitable  residences  for  living 
beings.  The  only  objection  to  this  view  is,  the  diflerence  in  the 
amount  of  heat  received  from  the  sun,  supposing  it  to  be  according  to 
the  inverse  ratio  of  the  squares  of  their  distances  from  the  sun.  But 
we  see  from  the  difference  of  temperature  on  the  eai-th,  at  the  base  and 
summit  of  high  mountains,  that  the  actual  heat  depends  much  upon  the 
modifying  circumstances,  as  well  as  upon  the  direct  rays  of  the  sun. 
And  we  have  reason  to  suppose  that  the  temi)erature  of  the  other 
planets  does  not  differ  much  from  that  of  the  earth. 

For  instance,  the  temperature  of  Mars,  as  indicated  by  the  melting 
of  its  snow,  and  that  of  Jupiter  and  Saturn,  as  indicated  by  the  amount 
of  vapor  in  their  atmosphere,  appear  to  be  similar  to  that  of  the  earth. 
Mercuiy  and  Venus  are  protected  from  the  direct  rays  of  the  sun  by 
dense  clouds.  Causes  unknown  to  us,  may  and  probably  do,  modify 
the  temperature  of  all  the  planets  in  a greater  or  less  degree,  suffi- 
ciently so,  for  the  purposes  of  animal  life.]  . 


HERSCHEL. 

This  planet  xvas  discovered  by  Sir  William  Herschel,  March  l.'Ifh, 
1781.  It  had  been  observed  by  Flarnstead',  Mayer,  Tycho  Brahe, 
and  other  astronomers,  and  was  regaided  by  them  as  a fixed  star,  and 
such  it  was  considered  by  Dr.  Herschel,  until  he  discovered  it  to  be  a 
planet,  from  its  having  moved  from  the  place  where  he  had  observed 
it  some  lime  before. 

Sir  William  Herschel  gave  it  the  name  of  “ Georgium  Sidus.  or 
Georgian  Star,”  in  honour  of  his  Royal  patron,  George  HI.,  but  the 
Royal  Academy  of  Prussia,  called  it  Uranus. 


THE  NEW  PLAInET. 

CAUSE  WHICH  LED  TO  ITS  DISCOVERY. 

It  had  been  found  by  observation,  that  the  attraction  of  the  planets 
upon  each  other,  accelerate  or  retard  the  motion  of  each.  These  varia- 
tions have  been  well  understood  by  astronomers  for  many  years  ; but 
it  xvas  found  by  a series  of  oljservations  made  during  several  years 
upon  the  planet  Herschel,  that  its  motion  in  the  heavens  xvas  affected 
by  some  cause  other  than  that  of  Saturn  or  Jupiter.  This  led  astrono- 
mers to  suspect  that  there  might  be  another  planet,  either  between  the 
orbits  of  Saturn  and  Herschel,  or  beyond  that  of  Herschel.  Leverrier, 
having  collected  the  obserx’ations  of  the  most  celebrated  astronomers  for 
many  years,  xx\as  enabled,  by  his  profound  knoxvledge  of  the  mathe- 
matics, to  calculate  its  elements. 


rt 


NEW  MOON 


NEW  MOON  OR 
INTCRlOR 
CON  J UNCTION 


MOON 


ThC  MOON  AS  SCtN  FROM  THC  EARTH 
AFRCARS  At  LAROCAATHB  SUN 


PmSllS!  Of  TIE  MOOIf 


rULL  MOON 


LAST  QUARTER 


ru  LL  MOON 
OR  OPPOSITION 


FIRST  QUARTET, 

f - J \ 

O J() 


IRST  aUARTEP. 


UST  QUARTER 


run  MOON 

OR  OPPOSITION 


APOGEE-  quarter\ 


MOON  >v 


\ F 


I rst  quarter  o 


last  Quarter 


FIG. 2 




PERIGEE 


FIG.  3 


1 L HI  S 'I'  II  A '1'  J<:  D 


LESSON  XXXIII. 

MOON. 

Qiicxtion.  WiiAT  is  the  moon  ? 

Amwer.  The  moon  is  a secondary  planet,  revolving 
around  the  earth. 

Q.  Is  tlic  moon  larger  or  smalh'r  than  the  earth? 

A.  It  is  49  times  less  than  the  earth. 

Q.  Wliat  is  tlie  diameter  of  the  moon  ? 

A.  2,180  miles. 

Q.  What  is  the  speeific  gravity  of  the  moon? 

]t  is  3-2  times  the  weight  of  water,  (3.37.) 

Q.  What  is  its  mean  distance  from  the  earth? 

A.  Two  hundred  and  forty  thousand  miles. 

Q.  In  wliat  time  does  the  moon  revolve  around  the  earth  ? 

A.  In  iibout  27-2  days,  (27(7.  Ih.  43/«.  115.5.) 

Q.  In  what  time  does  the  moon  revolve  upon  its  axis? 

A.  In  about  272  days,  or  in  the  stutie  time  that  it 
revolves  around  the  earth. 

Q.  What  is  the  result  of  the  moon’s  revolving  upon  its  axis  and 
around  the  eartli  in  the  same  time? 

A.  The  saute  side  of  the  moon  is  always  presented 
(o  (he  earth. 

Q.  Have  we  ever  seen  the  ofiposite  side  of  the  moon  ? 

A.  We  have  not. 

Q.  ^Vhat  causes  the  moon  always  to  present  the  same  side  to  the 
earth  ? 

A.  It  is  sujtp'osed  that  one  side  of  the  moon  is  more 
dense  than  the  other,  conseqtiently  the  centre  of  gravity 
is  not  in  the  centre  of  the  moon. 

qi.  What  is  a lunation,  or  lunar  month  ? 

A.  It  is  the  time  from  one  new  moon  to  another. 

Q.  What  is  the  length  of  a lunation  ? 

A.  About  29^  days.  (29(i.  12/i.  44772.) 

Q.  Why  is  a lunation  longer  than  the  time  it  takes  the  moon  to 
revolve  around  the  earth  ? 

A.  Because  the  earth  is  revolving  around  the  sun  at 
the  same  time.  (Fig.  3.  See  Note  1.) 

LESSON  XXXIV. 

Q.  What  is  the  length  of  the  days  or  nights  at  the  moon  ? 

A.  About  15  of  our  days.  (Note  4.) 

Q.  Which  way  does  the  moon  revolve  around  the  earth  ? 

A.  F rom  west  to  east. 

Q.  If  the  moon  revolves  from  west  to  east,  what  causes  it  to  rise  in 
the  east  ? 

A.  It  is  caused  by  the  earth’s  revolving  on  its  axis  the 
same  way.  (Note  2.) 

Q.  Does  the  moon  idse  the  same  hour  every  evening? 

A.  It  rises  about  50  minutes  later  every  day. 

Q.  What  is  the  cause  of  its  rising  .50  minutes  later  every  day  ? 

A.  It  is  caused  by  the  moon’s  revolving  around  the 
earth  from  west  to  east. 

Q.  What  causes  the  phases  of  the  moon,  from  new  moon  to  new 
moon  again? 

A.  It  is  caused  by  the  moon’s  revolving  around  the 
earth.  (See  Diagram.  Note  3.) 

Q.  When  is  it  new  moon  ? 

A.  When  the  moon  is  between  the  earth  and  sun, 
and  the  dark  side  is  presented  to  us.  (Fig.  1.) 


A S 'r  R 0 N O M Y . 3.‘i  J 


MOON. — Coivtiiiued. 

Q.  When  is  it  full  moon  ? 

A.  When  the  moon  is  upon  the  opposite  sid('  of  the 
etirth  frosn  the  sun,  and  the  illuminalt'd  side  is  pre- 
sented to  us.  (Fig.  1.) 

Q.  How  much  greater  is  the  light  of  the  sun  than  the  fidl  moon  ? 

A.  300,000  times  greater. 

Q.  When  are  the  sun  and  moon  in  quadrature  ? 

A.  When  they  are  ninety  degrees  distant  from  each 
other.  (Fig.  1.) 

Q.  How  much  of  the  illuminated  side  of  the  moon  is  visible  to  us 
when  it  is  in  quadrature? 

A.  One-half.  (Fig.  1.) 

Q.  How  much  larger  is  ..he  sun  than  the  moon  ? 

A.  70  millions  of  times  greater. 

Q.  Why  does  the  moon  ap])car  as  large  as  the  sun  ? 

A.  Because  it  is  four  hundred  times  nearer  to  us 
than  the  sun.  (See  Fig.  4.) 


Note  1.  Fig.  3. — The  moon  revolves  around  the  earth  in  about  27i 
days,  but  from  one  new  moon  to  another  it  is  about  29|  days;  this  dif- 
ference is  caused  by  the  earth’s  revolving  around  the  sun  at  the  same 
time  that  the  moon  is  revolving  around  the  earth.  This  will  appear 
plain  by  examining  Fig.  .3,  on  the  opposite  page.  If  we  suppose  the 
moon  to  be  in  conjunction  or  new  moon,  while  the  moon  is  revolving 
around  the  earth,  the  earth  moves  through  nearly  one-twelfth  part  of  its 
orbit,  and  when  the  moon  arrives  at  A,  it  will  have  made  a complete 
revolution  around  the  earth  ; but  the  moon  will  not  be  in  conjunction, 
or  between  the  earth  and  sun,  until  it  has  moved  the  distance  lioni 
A to  B — hence  it  will  be  seen  that  from  one  new  moon  to  another  the 
moon  has  to  make  more  than  one  complete  revolution  around  the  earth. 

Note  2. — That  the  moon  revolves  around  the  earth  from  west  to 
east,  from  one  new  moon  to  another  in  about  29A  days,  there  is 
not  the  least  doubt ; and  it  will  a[)pear  perfectly  plain  if  we  consider 
that  the  earth  is  revolving  on  its  axis  the  same  way,  or  from  west  to 
east ; the  earth  revolves  on  its  axis  in  24  hours,  whereas  the  moon  is 
29,2  days  in  revolving  around  the  earth  ; consequently  the  moon  only 
moves  from  west  to  east  in  24  hours,  as  much  as  the  earth  turns 
on  its  axis  in  50  minutes,  which  makes  the  moon  rise  as  much  later 
every  evening.  If  the  earth  did  not  revolve  upon  its  axis,  then  the 
moon  would  rise  in  the  west,  and  after  being  above  the  horizon  for 
nearly  15  days,  would  set  in  the  east,  and  would  be  below  the  horizon 
for  the  same  length  of  time,  when  it  xvould  rise  again  in  the  west. 

PHASES  OF  THE  MOON. 

Note  3.  Fig.  1. — By  phases  of  the  moon  is  meant  the  various  ap- 
pearances which  the  moon  presents  from  new  to  full  moon,  and  from 
full  moon  to  new  moon  again.  As  the  moon  is  a dark  body  of  itself, 
there  is  only  one-half  of  its  surface  illuminated  by  the  sun.  At  new 
moon,  when  the  moon  is  between  the  earth  and  sun  ; that  side  of 
the  moon  upon  which  tbe  sun  shines,  is  towards  the  sun,  and  the  dark 
side  is  presented  to  the  earth  ; consequently  we  do  not  see  any  portion 
of  the  illuminated  side  of  the  moon  at  new  moon,  see  Fig.  1 ; but  as 
the  moon  passes  around  from  west  to  east,  it  brings  the  illuminated 
side  of  the  moon  more  and  more  to  our  view  ; at  the  fii  st  quarter  we 
can  see  one-half  of  the  illuminated  surface,  and  when  the  moon  arrives 
at  full  moon,  we  can  see  the  whole  of  the  illuminated  surface,  as  the 
earth  is  then  between  the  sun  and  moon.  From  full  moon  to  nexv 
moon  again,  the  illuminated  surface  disappears  in  the  same  manner  as 
it  appeared. 

LETTG-TH  OF  THE  DAYS  AND  NIGHTS  AT  TEE  MOON. 

Note  4.  As  the  moon  revolves  on  its  axis  only  once  in  its  revolution 
around  the  earth,  it  continually  {U'esents  the  same  side  to  the  earth, 
and  there  would  be,  consequently,  only  one  day  and  night  in  each  revo-  ' 
lution  of  the  moon  around  the  earth,  or  the  day  and  night  would  each  be  [ 
nearly  fifteen  days  long.  j 


■4 


LS3/VV 


r— 


I L L U S '1'  li  A 'r  !•:  DAS  'i'  11  O N ()  M V . 


LESSON  XXXV. 

MOON. — Continued. 

Quesllon.  Has  the  moon  aii  atmosphere  ? 

Amiver.  Ver^  little  if  any. 

Q.  Wliat  is  th„  appearance  of  tlie  moon  wlien  vi<,‘\vod  with  a teles- 
cope ? 

A.  It  appears  covered  with  liglit  and  dark  spots  of 
various  sliapes. 

Q.  What  is  the  cause  of  this  appearance? 

A.  It  is  caused  by  the  mountains,  plains  and  valleys 
ill  the  moon. 

Q Wliat  are  the  ligiit  spots  ? 

A.  Mountains  and  elevated  land. 

Q.  Wliat  are  the  dark  spots  ? 

A.  Plains,  valleys,  &c. 

Q.  Has  the  moon  any  oceans,  seas,  or  large  bodies  of  water  ? 

A.  Not  upon  the  side  towards  tlie  earth. 

Q.  If  you  were  living  ujion  this  side  of  the  moon,  what  would  be  the 
appearance  of  the  earth  ? 

A.  The  earth  would  appear  like  a large  stationary 
moon. 

Q.  How  much  larger  than  the  moon  appears  to  us? 

A.  Thirteen  times  greater. 

Q.  In  what  time  would  the  heavenly  bodies  appear.to  revolve  around 
the  moon  ? 

A.  The  stars  would  appear  to  revolve  in  21  h.  days, 
the  sun  in  293  days. 

Q.  What  is  the  shape  of  the  moon’s  orbit  f 

A.  Elliptical,  or  one  diameter  greater  than  the  otlier. 
(See  Diagram,  page  24.) 

Q.  What  is  apogee  ? 

A.  It  is  the  point  in  the  orbit  of  the  moon  farthest 
from  the  earth. 

Q.  What  is  perigee  ? 

A.  It  is  the  point  in  the  orbit  of  the  moon  nearest 
to  the  earth. 

Q.  'When  is  the  moon  in  apogee  ? 

A.  When  it  is  at  its  greatest  distance  from  the  earth. 

Q.  When  is  the  moon  in  perigee  ? 

A.  When  it  is  nearest  to  the  earth. 

(}.  Has  the  moon  any  change  of  seasons  ? 

A.  None,  except  those  changes  which  take  place 
every  lunar  month. 


PHYSICAL  CONSTI'jlTJTION  OP  THE  MOON.  i 

Im  viewing  the  moon  with  the  naked  (>ye,  her  disc  appears  diversi- 
fied with  dai'k  and  bright  spots,  which  on  being  exaiiiinccl  with  a pow- 
erful telescope  are  discovered  to  be  mountains  and  valleys.  ’1  hi;  whole 
surface  of  the  moon  is  covered  with  these  sjiots,  which  is  evident  from  j 
the  fact  that  the  line  of  separation  between  thi!  illuminated  and  dark  j 
hemisiiheres,  is  at  all  times  extremely  ragged  and  uneven.  'I'he 
mountains  on  or  near  this  line  cast  behind  them  long  black  shadows, 
like  the  mountains  on  th’e  earth  when  the  sun  is  rising  or  setting.  I'he 
moon  is  a much  more  mountainous  body  than  the  eaith,  and  the  moun- 
tains are  vastly  higher  com[)ared  with  its  size  than  those  of  the  earth. 
(?ne  of  the  mountains  (named  I'lirha)  situatial  in  tin?  southeast  part  of 
the  Moon,  is  apparently  a volcanic  crater  .’)()  miles  in  diameter,  and  \ 
10.01)0  feet  deep,  with  a central  mountain  rising  to  the  height  of  \ 
.5,000  feet.  The  height  of  ten  of  the  jirincipal  mountains,  according 
to  the  recent  measurement  of  Miedler,  is  from  3?  to  41  miles.  'I'he 
mountains  of  the  moon  do  not  run  in  ranges  like  those  of  the  earth  ; 
but  are  single  peaks  scattered  over  nearly  the  whole  surface  of  the 
moon,  and  are  generally  of  a circular  form  shaped  like  a cup.  'J'hese 
facts  su})stantially  prove  the  mountains  of  the  moon  to  be  of  volcanic 
origin,  and  in  some  of  the  principal  ones,  decisive  marks  of  volcanic 
stratification,  arising  from  successive  deposites  of  eiect(‘d  matter,  may 
be  distinctly  traced  with  powerful  telescopes — 'I'he  moon  contains  no 
large  bodies  of  xvatei',  such  as,  oceans,  s(>as,  <Ac.,  especially  u])on  the 
side  visible  to  us.  If  there  are  any.  they  must  be  upon  the  opposite  side 
of  the  moon  which  is  never  presented  to  us.  'I'he  moon  also  has  very 
little  if  any  atmosphere,  at  least,  none  of  sufl'icient  density  to  refract  the 
rays  of  light  in  their  passage  through  it:  from  these  two  circumstances 
there  are  no  clouds  floating  around  the  moon  : if  theie  were  any,  they 
would  at  limes  be  visible  to  us,  Imt  none  have  been  observed,  it  pre- 
sents the  same  appearance  that  it  did  2,000  years  ago  ; no  trace  of 
vegetation  or  change  of  seasons  has  been  observed,  everything  ajtpears 
solid,  desolate,  and  unfit  for  the  support  of  animal  or  vegetable  life. 
Whether  the  materials  of  which  the  moon  is  composed,  are  of  the 
same  nature  as  the  earth,  there  are  no  means  of  knowing.  From  the 
effect  of  the  moon’s  gravitation  in  producing  the  nutation  of  the  earth’s  ; 
axis,  the  mass  of  the  moon  is  determined  to  be  very  nearly  l.SOth  of 
the  mass  of  the  earth,  whence,  as  her  volume  is  1.49th  of  the 
earth’s  volume,  it  follows  that  her  density  as  compared  with  the  mean 
density  of  the  earth  is  .01-5  or  a little  more  than  one  half;  consequent- 
ly the  materials  of  which  the  moon  is  composed  are  about  half  as  heavy 
as  the  same  bulk  of  the  earth. 

There  being  little  or  no  atmosphere  about  the  moon,  the  heavens, 
in  the  daytime,  have  the  appearance  of  night  to  the  inhabitants  of  the 
moon,  when  they  turn  their  backs  to  the  sun  ; and  the  stars  then  i 
appear,  as  bright  to  them  as  they  do  in  the  night  to  us  ; for  it  is  entirely 
on  account  of  the  light  which  our  atmosphere  reflects  that  the  heavens 
a[ipear  luminous  about  us  in  the  daytime.  If  our  atmosphere  were 
removed,  ortly  that  part  of  the  heavens  would  be  light  in  which  the  sun  | 
is  situated ; and  if  we  turned  our  backs  to  the  sun  the  heavens  would 
appear  as  dark  as  night.  The  light  which  the  full  moon  affords  us  is 
very  small,  when  compared  with  the  light  of  the  sun  ; it  being  300,000 
times  less.  It  has  also  been  demonstrated  that  the  light  reflected  by 
the  moon  produces  no  heat  ; as  its  rays,  when  collected  by  the  aid  ot  / 
the  most  powerful  glasses,  have  not  been  perceived  to  produce  the 
slightest  effect  upon  the  thermometer. 

IS  THE  MOON  INHABITED  ? 


Q.  What  is  the  harvest  moon  ? 

A.  When  the  moon  is  full  in  September  and  Octo- 
ber, it  rises  only  a few  minutes  later  for  .several  suc- 
cessive evenings,  and  thus  aflbrds  light  for  collecting 
the  harvest,  it  is  therefore  called  the  harvest  moon. 

Q.  What  is  the  cause  of  the  harvest  moon  ? 

A.  It  is  caused  by  the  moon’s  orbit  being  very  ob- 
lique to  the  liorizon. 

Q.  Is  the  moon  inhabited  ? 

A.  The  want  of  air  and  water,  render  it  uninhabit- 
able by  beings  like  ourselves. 


From  the  physical  constitution  of  the  moon,  it  is  evident  that  the 
moon  is  not  inhabited  ; at  least,  by  beings  constituted  like  ourselves. 
The  moon  having  no  atmosphere,  we  could  not  maintain  an  existence 
upon  its  surface  for  a single  hour  ; even  if  it  is  provided  with  the  other 
necessary  means  for  our  existence  : neverthless,  this  is  not  conclusive 
evidence  tha^t  the  moon  is  not  inhabited.  'Fhe  same  power  that  called 
the  moon  into  existence  could  as  easf^constilute  beings  fitted  to  inha- 
bit its  surface,  and  enjoy  an  existence  like  that  of  ours.  It  may  be 
very  properly  risked — if  the  moon  is  not  a habitable  body,  for  what 
urpose  was  it  created  ? This  is  a question  which  is  more  easily  asked 
lan  answered.  We  do  know  that  it  exerts  a powerful  influence  in 
raising  the  tides,  and  how  far  this  influence  operates  upon  the 'animal 
and  vegetable  kingdoms,  we  are  unable  to  decide ; its  influence  i:>  no 


WEST 


37 


I L L (j  s r ii  A 'i*  i:  i) 

I.  V.  S S ( ) N \ X X V 1 . 

ECLIPSES. 

Queslioii.  AVIiiit  is  an  ccli|)S(i? 

Answer.  It,  is  the  intc'rcoptioii  of  (lie  sun’s  rays  liy 
some  opake  body. 

Q.  Flow  are  eclipses  divided,  will)  respect  to  the  l)ody  ec]ij)scd  ? 

A.  Into  two  kinds,  solar  and  luiuir. 

Q.  AVhat  is  a solar  eclipse  ? 

A.  It  is  an  eclipse  of  the  sun. 

Q.  What  is  the  cause  of  an  ecli|>sc  of  the  sim  ? 

A.  It  is  ctuised  by  the  moon’s  pivssiiu?  lietween  (he 
earth  and  sun,  and  casting  its  shadow  upon  the  eiirtli. 
(P'ig.  3.) 

(^,  AVhen  must  an  eclipse  of  the  siin  take  jilace  ? 

A.  It  can  hajtpen  only  at  new  moon. 

(J.  What  is  a lunar  eclipse? 

A.  It  is  an  eclijise  of  the  moon.  (Fig.  3.) 

Q.  What  causes  an  eclipse  of  the  moon? 

A.  It  is  ciliised  by  the  moon’s  passing  (hrotigh  the 
earth’s  shadow.  (Fig.  3.) 

Q.  When  must  an  eclipse  of  the  moon  take  ])lace  ? 

A.  It  can  happen  only  at  full  moon.  (Fig.  3 nnd  4.) 

'' '.  How  are  eclipses  divided,  with  respect  to  the  amount  eclipsed  ? 

A.  Into  total  and  partial. 

Q.  " hat  is  a total  eclipse  ? 

A.  It  is  an  eclipse  of  (he  whole  of  (he  sun  or  moon. 
(I'ig.  3 and  8.) 

Q.  \Vhat  is  a partial  eclipse? 

i A.  It  is  an  eclipse  of  only  a part  of  the  sun  or  moon. 

! (Fi.t?- 

; Q.  What  is  an  annular  eclipse? 

A.  It  is  an  eclipse  of  the  central  part  of  the  sun,  when 
the  moon  is  so  I'ar  from  the  earth,  that  the  sun  can  be 
: seen  like  a bright  ring  around  it.  (Fig.  9,  Xote.) 

Q.  Do  we  have  an  eclipse  of  the  sun  at  every  new  moon  ? 

A.  We  do  not. 

(^.  Why  do  we  not  have  an  eclipse  of  the  sun  at  every  new  moon  ? 
A.  llecause  at  new  moon,  the  moon  is  generally  too 
‘ hiith  or  too  low  for  its  shadow  to  fall  upon  the  earth. 
Fig.  .5.) 

Do  we  have  an  eclii)sc  of  the  moon  at  every  full  moon  ? 
yl.  We  do  not;  at  lull  moon  the  moon  generally 
j)!issf‘s  tdtoce  or  below  (he  earth’s  shadow. 

What  is  the  lenfflh  of  the  earth’s  shadow  ? 

yl.  About  GOD, 990  miles.  (Note.  This  is  the  mean  or 

IIVIT.I'JC  Icii'^th.) 

O.  \\  tint  is  the  Iciieth  of  the  moon’s  shadow  ? 

yl.  About  231,999  tuiles.  (Note.  This  is  the  mean  or 
.ivt  r:ip-(;  length. j 

(-i.  \\  hat  i‘  a ? 

A.  It  is  (he  (wcifih  jtart  f)f  (h(!  apparent  diiimeter  of 
the  stiti  or  moon’s  <!!:'(•.  (rig.  ('>.) 

\\  hat  i tin'  prcalcsi  nutiile-r  of  (odipsc-.s  that  ean  take  place  in 
a yea  r t 

A.  r-oven  ; fiv(r  of  the  sun  iind  two  of  (he  moon. 

W hat  i)  the  least  nuinher  of  ccli|,'  '’''  that  can  take  place  in  a 

yi  a I ' 

A.  'I’wo  ; ruid  both  musl.  be  of  (he  sun. 


A S 'I'  It  ()  N It  M V . 


ECLIPSES.  I 

A 1,1,  o|)ake  bodies  c.nst  a shadow  when  the  I'.a  ys  from  .atiy  himinon~  j 
body  fall  upon  (hem.  livery  primary  and  .secondary  pl.anel  in  the  9 
solar  .system  casts  ti  sh.adow  low.ard.s  that  point  of  (he  hea\en.s  which  i j 
is  opposite  to  tin;  snn.  Il’  (he  sun  wme  .smaller  th.-in  the,  caith,  the  ^ 
e.'irth’s  shadow  would  inere.ase  in  dianwter  a-  the  di.-t.’ince  increase, 
from  the  earth,  (See  I je.  I ;)  lint  if  the  snn  and  earth  were  . f the  ! 
same  size,  the  shadow  wonid  be  of  the  same  si/e,  no  niattej'  how  great  ' 
(he,  distance  from  the  earth,  (See  I’ig.  ^ I’ni  ||„.  snn  is  im- 
mensedy  larger  that)  the  earth,  (lie  earth’s  tiTidow  (erniinates  in  a point 
at  about  (lot), otto  miles  from  the  earth;  the,  length  of  the  e.iith’s  i 
shadow  is,  howevi  r,  subject  to  considerable,  variation.  When  the  i 
earth  i.s  nearest  to  the  sun,  \\hi<di  takes  place  about  .lannaiy  Isi,  (he 
shadow  is  rnucdi  shorter  than  u lnm  (he  earth  is  at  its  greatest  rli.stance, 
which  i.s  about  the  1st  of  .July.  'I'hc  moon  revolves  around  the  eaitli 
in  about  days,  from  one  new  moon  to  another.  If  the  moon 

jiassed  at  evm-y  new  moon  exactly  between  the  centres  of  the  .sun  and 
earth,  we  should  have  a great  e<di|>se  of  the  sun  at  ^ver\  new  moon, 
and  a total  eclipse,  of  (he  moon  at  every  tiill  moon,  (.See  I'ig.  b ;)  but 
(he  moon’s  orbit  or  path  makes  an  angle  with  the  plane  of  tin-  eidiptic, 
(the  plane  of  the  ecliptic  is  de.scribed  by  a line  drawn  from  the  centre 
of  the  sun,  passing  through  the  centre  of  (he  earth  and  extended  (o 
the  heavens,)  of  about  .b)  degrees,  comseipiently  one  half  of  (he,  moon’s 
orbit  is  above  the  ecliptic,  .and  the,  other  half  i.s  below  it. 

'I’lie-  two  opposite  points  where  the,  moon’s  orbit  cuts  the  plane  of  the 
ecliptic,  are  calh'd  the  moon’s  nodes;  the  nodes  do  not  keep  in  the 
same  position  with  respect  to  the  earth  and  sini,  but  have  a retrograde 
motion  of  about  10  degrees  in  a year.  'I'his  causes  the  irioon  at  new 
moon  to  be  too  high  or  too  low,  so  that  (he  moon’s  shadow  pa.sses 
above  the  north  pole  or  Indow  the  south  jiole,  hence,  theie  is.no  ecli|i.se, 
and  at  full  moon,  the  moon  passes  edther  above  or  below  the  earth’s 
shadow.  A total  eclijise  of  the  moon  ‘occurs  when  the  wdiole  of  the 
moon  is  immersed  in  the  earth’s  slunlow’,  (.See  i''ig.  'i  ;)  but  w'c  occa- 
sionally have  a partial  eclijise  of  the  moon  wdiich  is  caused  by  the, 
moon’s  being  so  high  or  so  low'  as  only  to  be  jiartially  immersed  in  the 
earth’s  shadow,  (See  Fig.  4.)  'i'he  diameter  of  tin',  sun  and  moon’s 
discs  is  divided  into  twelve  etpial  parts,  called  digits  (See  Fig.  fi  ;)  but 
by  ins|)ecting  the  diagram,  it  will  be  seen  that  when  the  snn  is  said  to 
have  six  digits  eclipsed,  that  only  about  one  third  of  the  di.^c  of  the,  snn 
is  covered  by  the  moon,  although  one  half  of  the  diameter  of  the  sun  is 
hidden  from  view.  The  sun  and  moon  ajijiear  to  be  about  the  same 
size,  but  the  apparent  size  of  both  is  subject  to  some  variation  ; xvhen 
the  earth  is  in  that  point  of  its  orbit  nearest  the  sun  (.tanuary  1st,)  the 
sun  appears  larger  than  at  any  other  time  during  the  year,  and,  when 
the  moon  is  at  the  greatest  distance  from  the  earth,  she  appears  the 
smallest.  If  an  eclipse  of  the  sun  should  take  [dace  exactly  at  this 
time,  the  shadow  of  the  moon  would  terminate  in  a jioint  before  it  reached 
the  earth,  and  the  moon  would  not  appear  large  enough  to  cover  the  ' I 
whole  disc  of  the  sun,  but  would  produce  what  is  called  an  annular 
eclipse,  or  the  sun  xvould  appear  like  a luminous  ring  around  the  moon, 
(Sec  F'ig.  9;)  but  if  the  earth  was  at  its  greatest  distance  from  the  sun 
(July  1st)  and  the  moon  the  nearest  to  the  earth,  then  the  moon  w'onld 
apjiear  larger  than  the  sun,  and  the  shadow  of  the  moon  w'ould  touch 
the  earth  before  it  terminated  in  a point;  tliisw'ould  jiroduce  a total  and 
as  great  an  eclijise  of  the  sun  as  can  take  place,  (.See  I'ig.  3.)  A 
total  eclijise  of  the  sun  is  visible  only  to  a small  portion  of  the  eai'th  at 
one,  and  the  same  time,  the  shadow  of  the  moon  where  it  touche's  the 
earth  would  be  only  about  l.aO  miles  in  diameter,  conseijuently  th.ere 
would  be,  only  a space  aci'oss  the  earth  from  w’est  to  cast  about  ^.ot) 
miles  wide,  in  which  it  would  ajipear  total,  but,  a partial  eclipse  would 
b('  seen  from  a space  more  than  2,()0t)  mih's  wide  on  each  side  of 
the  umbra,  or  dark  shadow'.  'I'hose  who  lived  north  of  the  dark 
shadow'  w'oiild  see  the  southern  portion  of  the  sun  eclijised,  and  those 
who  lived  south  of  it,  W'ould  see  the  northern  limb  of  the  sun  eclijised. 

Melijises  of  tin'  sun  are,  more  iVi'ijnent  than  of  (he  moon,  because 
the  sun’s  ('cjijitic  limits  are  greater  than  the  moon’s,  yet  w'e  have  more 
visibh'  (‘(dijises  of  (he,  moon  than  of  (he  sun,  because  eclijises  of  (ho 
moon  are  visible  from  all  j)ar(.s  of  the  earth  where  the  moon  is  above 
the  horizon,  and  are  e(jually  great  to  each  (>!'  those  jiarts  ; but  eidijises 
ol’  (he  sun  are  visible  only  to  those  [daces  upon  which  the  moon's  i 
shadow'  lulls. 


40  1 1,  I.  U S I{  A 'I' [•:  I)  A S 'I' li  ()  N ()  M V . 


ECLIPSES.-  Continued. 


Qiieslion.  Why  .ire  tliero  niore  t'r.lip.scs  of  tlic  Sun  tli.Tii  of  tlic  Moon  ? 

Anstver.  J^ecuuse  tlie  Solar  jM’liptic  Limit  is  10^ 
degrees  greater  than  that  of  the  Moon. 

Q.  Are  visible  eclipses  of  the  Moon  iiioro  fretjuent  ,'it  any  particular 
place,  than  those  of  the  Sun  ? 

A.  They  are  ; beetuisc  an  eclij>se  of  the  IVloon  is 
visible  and  apj)ear.s  tis  grctit  to  all  ])lace.s  on  the  J^arfh 
■where  the  Moon  is  above  the  horizon. 

Q.  M'hy  are  not  visible  eclipses  of  the  Sun  as  frequent  as  those  of 
the  Moon  '( 

A.  Because  an  eclijtse  of  the  Sun  is  A'isilile  only  at 
those  places  on  the  Earth  Avhere  the  Uml)ra  or  Pen- 
umbra hills. 

Q.  What  is  the  Umbra  of  the  Eai  th,  Moon  or  any  other  planet  ? 

A.  It  is  tlie  /o/aZ  dark  shadow  of  the  planet,  see  b'ig- 
1,  2,  3,  4. 

Q.  M'hat  is  the  Penumbra  ? 

A.  It  is  a faint  shadow  surrounding  the  Umbra,  Fig. 
1 2 3 4 

Q.  What  is  the  extent  of  the  Moon’s  Umbra  ui)on  the  I'huth  when 
! greatest  ? 

A.  It  never  can  exceed  175  miles  in  diameter,  and 
it  generally  is  much  less,  see  P^ig.  3. 

Q.  Why  do  eclijises  of  the  Sun  always  begin  on  the  western  side 
i of  the  Sun '? 

: A.  Because  the  Moon  passes  from  A’cest  to  east  be- 

I tween  the  Earth  and  Sun. 

I Q.  M'hy  do  eclipses  of  the  Moon  begin  on  the  eastern  side  of  the  Moon  ? 

I A.  Because  the  Moon  passes  from  west  to  east 

through  (he  Etirth’s  shadow,  see  Fig.  1. 

Q.  In  what  direction  does  the  Moon’s  shadow  pass  over  the  Earth 
in  a .Solar  Eclipse  ? 

A.  It  passes  over  the  earth  from  west  to  east. 

Q.  flow  large  a portion  of  the  Earth’s  surface  may  be  covered  by 
the  Aloon’s  Penumbra? 

A.  A space  about  4,393  miles  in  diameter. 

Q.  tVhy  are  not  all  eclipses  of  the  Sun  total? 

' A.  Because  the  Moon  being  so  far  from  the  Earth, 
its  slnidow  terminates  in  a point  before  it  reaches  the 
earth,  see  Fig.  2. 

; Q.  In  what  point  of  its  orbit  must  the  Moon  be  to  cause  a total 
! eclipse  of  the  Sun  ? 

' yl.  It  must  be  at  or  near  its  jperi^ee,  when  (he  Um- 
bra of  the  Moon  would  reach  the  Earth,  see  Fig.  3. 

. How  long  m.ay  an  eclipse  of  the  Moon  continue? 

A.  It  may  conlinue  four  hours;  in  (his  case  tlie 
Moon  must  pass  tlireclly  through  the  centre  of  the 
! Eart Ids  shadow,  see  Fig.  I. 

Q.  Ih  the  Moon  ever  vi.-iblo  when  it  is  tof.-illy  eclipsed? 

A.  it  is,  and  ajijiearsofa  reddish  color  like  tarnish- 
od  cojiiu  r. 

\\  liai  (•;iui‘cr,  the  Moon  to  lie  vi  ililo  when  it  is  totally  (udipsed  ? 

A.  'Ilie  rays  ol  the  Stin  in  [»iissitig  (lirttiigh  (lut 
at  niosplicrc  ol  the  liaith  ttrt'  rcliactcd  or  turned  out 
of  tludr  foiijM-  atid  lalling  upon  (he  .Moon  render  it 
laintlv  visihh-. 


liat  ai'C  the  edects  of  ,a  tot;il  eclipse  of  the  .'S|iri  ? i 

A.  'I  he  heitvens  :ire  shrouded  in  darkness,  so  that 
the  stiirs  and  platiets  hecome  visible;  the  tiiiimal 
tribes  iMM’onut  iigittitcd  ; and  :i  general  gloiun  over-  ' 
spre.ids  the  lan<lscii|)e.  1 

Q.  II  ow  unH  tfil.'il  of  the  Sun  coiititiue  ;it  uiiy  iun*  ^ 

f)lace  on  the  earth  ? ; 

A.  A totiil  eclipse  of  the  Siiti  ctuinot  eontinne  til. 
any  one  jtlace  over  four  miniilt's.  | 

W hy  is  the  dark  portion  of  tlie  -New  Moon  visible  wlien  sei'ii  in 
tlie  west  .soon  after  tlie  .Sun  is  set  ? 1 

yl.  Bt'Ciuise  tin'  niys  of  the  Sun  fiillitig  iifton  tin;  i 
r'afth  iU't'  relleclt'd  hiiek  njton  tin;  dark  portion  ol  the  | 
M oon  and  render  it  lltinllv  visible,  set'  Fig.  4.  ['I'l  lis 

iippciirtince  of  tin*  Moon  at  new  moon  is  sometimes 
(‘ill It'd  ‘Who  Old  Moon  in  fhe  N-"W  Moon's  amis.”] 

(2-  Are  tlie  Sf.ars  or  planets  ever  bidden  Ironi  oiir  view  by  tlie  Mofiii  ? i ’ 

A.  They  fretiiK'iil ly  iire,  which  is  ciilled  the  Occnl-  i 
ta(ion  of  a star  or  jiliinet. 


ECLIPSES.  ! ; 

Eci.ipsks  are  among  the  most  inloresling  plionomona  prosoritoil  to  us  hy  the  lioavouly  ‘ , 
bodie.s.  In  all  ages,  when  an  eclipse  lia.s  taken  place,  it  has  l•xcile(i  the  pri.fi.imd  alien-  ! | 
tioii  ol  the  learned,  and  the  fears  and  suis-r.-lilimis  of  the  ignorant,  't  he  causes  of  4 
eclipse.s  before  the  seveiileenth  centnr/V  ere  known  only  to  a tew,  and  they  generally  i ' 
took  advantage  of  this  knowledge  to  impose  upon  the  credulity  of  the  ignorant  by  pre-  i , 
tending  that  they  were  inspiied  by  the  Gods.  Among  the  ancienr  nations,  tlie  filial-  ' 
deans  were  the  foremost  in  tlieir  observations  of  the  phenomena  of  the  In-avens  ; per-  ' : 
haps  this  was  owing  in  some  measure  to  lln-ir  occnpalioii  ; They  being  she|;heids  were  I 
obliged  to  watch  their  flock.s  hy  night  to  proieci  them  from  the  wild  hea.-t-  winch  were  | 
at  that  lime  numerous.  Men  under  such  circumstances  would  naturally  be  h-d  to  watch  | 
closely  the  movements  of  the  heavenly  bodies,  and  more  e.specially  so  ; for  in  the 
earlier  periods  of  the  world  they  had  no  correct  mode  of  recKoniiig  time  in  order  to 
determine  the  seasons  or  the  [iroper  seed  time  and  harve.vt. 

Eclipses  attracted  the  particular  attention  of  the  Chaldeans,  and  by  a series  of  ob- 
servations extended  through  several  centuries,  they  discovered  a very  imiiortant  fact 
relating  to  eclipses  although  they  did  not  understand  the  cause. 

By  comparing  the  records  which  had  been  made  for  a great  length  t.f  time,  they 
found  that  a certain  period  of  time  elapsed  between  eclipse.s  of  the  same  kind  and 
magnitude  ; that  is,  if  18  years,  11  days,  7 hours  and  -hi  minutes,  were  added  to  the 
time  of  the  happening  of  any  eclipse,  it  would  show  the  time  of  the  return  of  tlie  same 
eclipse  ; the  only  difl'erences  would  be  that  it  would  not  happen  at  the  same  lime  in 
the  day  and  it  would  be  a little  greater  or  less  than  the  previous  eclipse — thus  they 
were  able  to  predict  eclipses  with  sufficient  accuracy  to  answer  their  designs  upon  the 
ignorant  without  understanding  the  laws  by  v.’hieh  these  periodica!  returns  were 
produced. 

To  explain  this  briefly,  it  must  be  remembered  that  the  moon’s  orbit  makes  an  anfle 
with  the  plane  of  the  earth’s  orbit  of  51“;  tliese  two  points  where  the  moon’s  orbit 
cuts  the  plane  of  the  earth’s  orbit,  are  called  nodes,  (see  diagram,  greatest  number  of 
eclipses  in  one  year,  page  45).  Now  we  will  suppose  that  on  any  day  at  noon  it  is  new 
moon,  and  the  moon  is  just  16°  degrees  from  her  descending  node,  the  shadow  of  the 
moon  would  just  toKcli  the  earth  at  the  north  pole  ; in  223  lunations  or  18  years,  11  days, 

7 hours,  -!3  minutes  thereafter,  the  moon  would  come  nearly  to  the  same  position  as  it 
was  at  the  beginning,  consequently  there  would  be  another  small  eclipse  of  the  Sun, 
and  at  fhe  expiration  of  every  223  lunations  it  would  return,  and  at  each  return  the 
moon’s  shadow  would  pass  across  the  earth  a little  more  to  the  south  until  the  eclipse 
had  appeared  about  77  times,  when  it  would  pass  ofl' at  the  south  pole,  occupying  a 
jieriod  of  1388  years  : The  same  period  would  not  commence  again  until  the  expiration 
of  12192  years.  Each  eclipse  which  takes  j.lace  during  any  year,  belongs  to  a separate 
and  similar  period.  Those  periods  of  eclipses  which  come  in  at  the  Moon’s  a.vcending 
node,  first  come  on  to  the  earth  at  the  south  ixile  and  at  each  return  the  moon’s  shadow 
passes  across  the  earth  more  to  the  norih  and  after  appearing  about  77  times  they  finally 
leave  the  earth  at  tli"  north  pole. 

Ill  those  periods  of  eclipses  of  the  moon  whicn  come  in  at  the  moon’s  descending 
node,  the  moon  first  touches  the  upper  portion  of  the  earth’s  shadow  and  at  each  return 
the  moon  pas.ses  through  the  earth’s  shadow  more  to  the  south  and  at  the  thiily-second 
reliirn  ihe  moon  would  uass  directly  through  the  centre  of  the  earth’s  shadow,  produc- 
ing a great  eciip.se  of  the  moon  ; also  in  those  eclipses  of  the  moon  which  come  in  at 
Inc  inomTs  ascending  node,  the  muon  first  conies  in  contact  willi  the  lower  portion  of 
the  earth’s  slindnw  and  at  eaidi  return  the  moon  passes  throngli  the  shadow  rnnre  to  the 
noilli  anil  gnes  thiongh  a .similar  coui'.se  as  in  the  former  case  ; it  nmst  he  remembered 
that  llieic  arc  a ninnher  of  eclipses  in  each  year,  the  greatest  nnmher  is  seven  the  least 
two  ; hut  the  eelipscH  which  liappeii  in  any  one  jear  cannot  take  place  again  until  the 
cxpirali'iji  of  IS  ymirs,  II  days,  7 hours,  Jo  minutes. 


i -12  ILF.  IJS'rUA'J’l'D 

i 


LESSON  XXXVII. 


MOOIT’S  NODES. 

Question.  What  an;  nodc.s  ? 

Ansiver.  They  arc  two  opposite  points  an  liere  the  orl>it 
of  ilic  moon,  or  any  other  planet  intersects  the  plane  of 
! (he  earth’s  orbit  or  ecliptic. 

jj  Q.  W liat  angle  dons  ttic  moon’s  orliit  malte  willi  itie  plane  of  the 
Ij  eartli’s  orldt  or  ('nliptic. 

ij  yI.  About  5i  deirrees.  (5°  S' 48".) 

; j Q.  What  ]):irt  of  the  moon’s  orl>it  is  iihove  or  norili  of  llin,  plane  of 
1 1 the  earth’s  orhit  ? 

!|  A.  One  hair,  tlie  other  lialf  being  below,  or  south  of 
} I he  earth’s  or!)it 

j Q.  Wliat  is  tlie  asrending  node? 

1 yl.  It  is  (Iiat  point  wliere  the  moon  passes  (lie  jilane 
I ol  the  earth’s  orlut  from  soulli  to  north. 

I (J.  WFiat  is  tlie  desnending  node  ? • 

jj  A.  It  is  (hat  jAoint  where  (he  moon  jtasses  the  plane 

ji  (it  the  earth’s  orbit  from  north  to  soutli. 

j ■ 

I j Q.  Do  the  nodes  cliange  their  position  as  regards  a fixed  [loint  in  the 
ij  lieavens? 

jj  A.  They  liave  a retrograde  motion  of  about  19  degrees 
ji  in  a year. 

Q.  .V'dipii  is  the  moon  in  north  latitude  in  the  heavens? 

yl.  W hen  it  is  north  of  the  earth’s  orbit  or  ecliptic. 

Q.  When  is  the  moon  in  south  latitude  in  the  heavens  ? 

A.  When  it  is  soutli  of  the  etirth’s  orbit  or  ecliptic. 

' Q.  What  is  the  greatest  latitude  of  the  moon  ? 

; A.  5)  degrees  north  or  south  of  the  earth’s  orbit  or 
ecliptic. 

Q.  What  is  the  greatest  declination  of  the  moon,  or  its  distance  north 
•ir  south  of  the  eipiinoctial  or  eijuator  ? ‘ 

c yl.  About  285  degrees. 

LESSON  XXXVIII. 

Q.  IIow  near  one  of  the  nodes  must  the  moon  be  at  new  moon  to 
cause  an  eclipse  of  the  sun  ? 

A.  Within  seventeen  degrees.  (16“  59".) 

Q.  How  near  one  of  the  nodes  must  the  moon  be  at  full  moon  to 
■ ! can«e  an  eclipse  of  the  moon  ? 

A.  About  12  degrees.  (1 1°  25'  4".) 

; Q.  If  the  moon  is  exactly  in  one  of  her  nodes  at  new  or  full  moon,  j 
,,  w!:at  kind  of  an  eidijisi;  ^^■ill  it  cause?  I 

; .1.  It  will  cause  ti  great  eclipse  of  the  sun  or  moon. 

‘ i (^.  ^V'hat  is  the  extent  of  the  solar  ecliptic  limit  in  which  an  eclipse 

; ol  'lie  : ;iii  can  take  place  ! 

/I . 'i’hirly-four  degrees,  seventeen  degrees  on  each 
■ i'le  of  fit  her  nod(‘. 

O.  What  ii  the  (!Xtetil  of  tln^  lunar  ecliptic  limit  in  which  an  eclipse 
i III  I he  moon  can  take  place  ? 

4. 'I'\\cnty-f<mr  degrees,  twelve  on  etich  side  of 
’ ( it  her  node. 

inrninon  and  surnnion  oonjuwotion. 
ij  Ifow  many  kind,'!  of  conjiiiiclion  are  (hero? 

!l  ,4.  'Two;  inffri(»r  iind  Miperior. 

^ Winn  i,  a p!aiiil  in  ind'iior  eonjunclion  with  the  sun? 

.4.  When  il.  is  bclween  (he  fiirlh  and  sun. 


A S 'I'  It  0 i\  0 IM  V. 


CONJUITCTION.— Continued. 

(t.  What  planets  can  be,  in  infi-rior  coiipmclioti  ? 

A.  Mercury  and  Venus;  .also  the  moon. 

().  When  are  two  planets  in  superior  conjunction  ? 

A.  \V  hen  they  :ir(‘  on  opposite  sides  of  (he  snn. 

(J.  What  planets  can  be  in  superior  eonjiinetion  with  the  sun  ? 

yl.  All  tlie  |)hme(s,  except  (he  earth  and  moon. 

I.ESSON  X X XI  X.  ^ 

INFERIOR  AND  SUPERIOR  PLANETS. 

Q.  IIow  are  the  primary  planets  di\  ided  ? 

yi.  'I’hey  tire  dit  iiled  into  two  (da.sses,  inferior  and 
snpiu'ior. 

Q.  Which  are  the  infi-rior  planets? 

yi.  Mercury  :md  Venus. 

(^.  ^>’hv  are  they  called  inferior  planets  ? 

yi.  Ilecanse  their  orbits  are  within  the  orhit  of  lint 
Ciirl  h. 

().  Which  are  the  superior  jilanefs  ? 

yl.  Miirs,  “/he  yi,s/eroi(I.s,”  .Injiiter,  S.atnrn,  Iferschcl 
and  i.everrier. 

(J.  Why  are  they  called  superior  [ilanets  ? 

yl.  Lecause  their  orbits  are  grcjitcr  than  the  orliit  of 
the  earth. 

EELIOCENTRIO  AND  GEOCENTRIC  LATITUDE  AND  LONGITUDE. 

Q.  What  is  the  Heliocentric  latitude  and  longitude  of  a planet? 

yi.  It  is  its  liilitude  and  longitude,  as  seen  from  the 
sun.  (See  Diagram.) 

Q.  What  is  the  Geocentric  latitude  and  longitude  of  a planet? 

yl.  It  is  its  latitude  and  longitude  as  seen  from  the 
earth. 

Q.  Does  a planet,  seen  from  the  earth,  appear  to  hax^e  the  same 
longitude  as  it  would  have  if  seen  from  the  sun  at  the  same  time? 

yl.  It  does  not,  unle.ss  tlie  eartii  is  between  the  sun 
and  planet. 


It  xvill  be  seen  by  inspecting  the  diagram  upon  the  opposite  page, 
that  there  are  two  small  circles  introduced  into  the  diagram,  the  white 
circle  which  represents  the  moon’s  orbit,  and  the  shaded  circle  which 
lies  in  the  plane  of  the  earth’s  orbit  or  ecliptic  ; this  shaded  circle  is 
introduced  into  the  diagi;;im  only  to  show  the  two  points  xvhere  the 
moon’s  orbit  intersects  the  jjlane  of  the  earth’s  orbit  or  ecii[)tic ; these 
two  points  are  called  the  moon’s  nodes ; the  point  where  the  moon 
passes  from  the  south  to  the  north  side,  or  above  the  earth’s  orbit,  is 
called  the  ascending  node  ; and  the  opposite  point,  or  where  the  moon 
descends  below  the  earth’s  orbit,  is  called  the  descending  node  ; the 
line  passing  through  the  centre  of  the  cai  th  from  one  node  to  the  other, 
is  calk'd  the  “ Zme  of  the  nodes.”  It  xvill  be  seen  also  that  one  lialf  of 
the  moon’s  orbit  is  above  the  plane  of  the  earth’s  orbit,  and  the  other 
half  below  it. 

'I'he  planets  Mercury  and  Venus  are  called  inferior  planets,  liecause 
their  orliits  are  within  that  of  the  earth,  and  of  course  nearer  to  the  sun. 
'I'he  other  primary  planets.  Mars,  Asteroids,  Jupiter,  Herschel  and 
Leverrier,  are  called  superior  jilanets  for  the  same  reason  that  their 
orbits  are  greater,  or  outside  that  of  the  earth. 

It  will  be  seen  by  inspecting  the  diagram  upon  the  opposite  page, 
that  tlie  planets,  seen  by  two  observers  at  the  same  time,  one  u])on  tlie 
sun  and  (he  otlier  upon  (he  eartli,  would  not  appear  to  be  exaetiy  in  the 
.same  point  of  the  heavens.  'I’lie  helioeentrie  longitude  of  a planet 
is  where  it  would  ap|iear  to  be  if  seen  from  llio  sun.  and  the  geocentric 
longitude  of  a |)laiiet  is  its  longitude  as  .seen  (Voin  the  earth. 


43 


41 


I 1.  I-  U S 'r  R A T !•:  DAS  'I'  R O N ()  M V . 


l.ESSON  xr.. 

GREATEST  NUMBER  OF  ECLIPSES  IN  A YEAR. 

()iirsti()7i.  W hat  is  llio  frrcaUist  iiiiiiiljor  of  ('c'lij)sc.s  lliat  ran  laUi; 


place  in  a year  ? 

Ajiswcr.  Seven  ; live  of  the  snn  iuid  two  of  the  moon. 

Q.  AVliat  is  the  least  number  of  ecli|)ses  that  can  lake  pliico  in  a 
year? 

A.  Two;  both  of  llie  sun. 

Q.  W'hat  must  he  the  position  ol'  the  mf)on  and  hc'r  aseendiTig  node, 
on  ihe  first  day  of  January,  to  cause  seven  eedipses  in  a )’ear? 

A.  It  must  be  new  niotm,  ami  (he  moon  must  be 
■within  17  degrees  of  her  asctuitliiig  node  at  the  time. 

Q.  Wdien  would  the  second  cclips(‘  lake,  |)lac('  ? 

A.  The  second  eclijtse  u ould  be  of  the  moon,  January 
15th,  at  her  descending  node. 

Q.  When  would  the  third  eclipse  take  place  ? 

A.  The  third  eclijtse  would  be  of  tlic  sun,  January 
29th,  at  the  moon’s  ascending  node. 

Q.  W^hen  the  fourth  eclipse 

A.  The  fourth  eclijtse  would  be  of  the  sun,  June  26th, 
at  the  moon’s  descending'node. 

Q.  W'hen  the  fifth  eclipse  ? 

A.  The  fifth  eclipse  w'ould  be  of  the  moon,  July  1 1th, 
at  her  ascending  node. 

Q.  W’hen  the  sixth  eclipse? 

A.  Tlie  sixth  eclipse  would  be  of  the  sun,  July  25th, 
at  the  moon’s  descending  node. 

Q.  'nen  the  seventh  and  last  eclipse  ? 

A.  The  seventh  eclijise  would  be  of  tlic  sun,  Decem- 
ber 20lh,  at  the  moon’s  ascending  node. 

0.  Why  are  there  no  eclipses  in  this  case  from  January  29th  to 
June  2Gth  ? 

A.  Because  the  moon  is  so  higli  at  new  moon  that  its 
shadow  passes  above  the  north  pole,  and  at  full  moon, 
tlie  moon  passes  below  the  earth’s  sliadow. 

Q.  Why  are  there  no  eclipses  in  this  case  from  July  2oth  to  Decem- 
ber 20lh  ? 

A.  Because  the  moon  is  so  low  at  new  moon,  that  its 
sh'ridow  passes  below  the  south  pole,  and  at  full  moon, 
the  moon  passes  above  the  earth’s  shadow. 

Q,  What  must  be  the  position  of  the  moon  and  tier  ascending  node, 
on  the  1-t  day  of  January,  to  cause  only  two  eclipses  during  the  year? 

A.  It  must  be  now'  moon,  tuid  the  moon  must  be  in 
or  very  mnir  her  ascending  node. 

f /.  Ilo'v  often  are  there  seven,  or  only  two  etdiftses  in  a year? 

A.  Not  ofleiier  tlnin  onc.e  in  a hundred  years. 

O.  W hat  is  the  rriost  common  numlau'  ofecIi))scs  in  a year? 

A.  I'our. 


Greatest  Number  of  Eclipses  in  a Year. 

Win.',  tlie  moon  i'-  within  17  deerei..  of  cither  node  at  tiew  niooti,  it 
will  eatne  ati  el  lipse  of  the  Miti,  and  wheti  Ihe  moon  is  within  12 
deen-r.  o(  eilh'  r node  at  lull  moon,  the  moon  will  then  be  more  or  les.s 
ei  |ip,e(|.  If  the  line  o(  the  nolle'.'  were  eaiTied  parallel  to  itself  around 
ihf  oil,  there  '.voiild  lie  pe.l  hall  .a  year  from  the  lime  of  one  node 
pi  in;'  the  uii.  III  the  other’  coming  around  to  the  sun;  but  tis 


the  nodes  have,  a rclro,grade  motion  of  alioiil  nineleen  degrecB  in  n yejir, 
it  is  only  177  days  from  the  conpinction  ol  one  nmle  to  the  ciinpineiion 
ol  the  other,  therefore,  in  whatever  time  of  the,  year  we  have  eciipscs  of 
the  sun  or  moon  at  either  node,  we  may  be  sure  that  in  177  days,  we 
shall  Inive  eclipse.s  about_  the  other  node.  If  we  sup|iose  the  moon  tit 
new  moon  to  be  17  degrees  from  her  ascending  node  on  the  first  day 
ol  January,  there  would  be  a small  eclipsi*  of  the.  sun,  and  at  the.  next 
ftill  moon,  January  Ibih,  there  would  be  a total  eclipse  of'the,  moon  ; as 
the  moon  would  be  only  about  2 degrees  from  the  descending  node  ; at 
the  next  new  moon,  January  2t)th,  the  moon  would  then  be  about  12 
degrees  upon  the  other  side  of  the  ase.ending  node,  which  would  ctinsc 
another  smtill  eclipse  of  the  sun, — hence  we  would  liiive  two  small 
eclipses  of  the  sun  Jit  the  a.'-eending  node,  and  one  great  eidipse  of  the 
moon  at  the  descending  node,  from  Jjiniiary  1st  lo  January  29th.  (See 
Dijigram.)  At  every  subseipnmt  new  moon,  the  moon  would  lie  so 
high  that  the  sluidow  would  jiass  above  the  north  pole,  jind  at  every 
fiill  moon,  the,  moon  would  jiass  below  the  earth’s  shadow,  until  June 
2(ith,  when  the  moon’s  descending  node  would  come  around  to  the,  sun, 
(see  Diagrjun  ;)  at  this  time,  the  moon  would  lie  about  7 degrees  froiri 
her  descending  tiode  ; this  would  cause  jiniilhcr  eclijise  of  the  sun.  At 
the  next  fiill  moon,  July  1 1th,  there  woiihl  be  another  total  eidijise  of 
the  moon  ; again,  at  thi-  next  new  moon,  July  2rjth,  the  moon  would 
still  be  within  17  degriu's  of  her  descending  node,  which  would  [irriduce 
another  small  eclijtsi'  of  the  sun. 

From  July  2.7th,  thei'c  would  be  no  cidipses  of  the  sun  or  moon,  as 
at  every  subseijiauit  new  moon,  the  moon  would  be  so  low  th.at  the 
sliJulow  of  the  moon  would  jiass  below  the  south  pole,  and  :it  every  full 
moon  the  moon  would  jiass  above  the  earth’s  shadow,  until  December 
2()lh,  when  the  ascending  node  would  come  arouiifl  agJiin  to  tlic  sun,  and 
at  the  I2th  new  moon  in  the  year,  the  moon  would  agjiin  be  within  17 
degrees  of  her  ascending  node  ; wo  would,  therefore,  have  another 
small  cclijise  of  the  sun,  which  would  be  the  seventh  and  last  eclijise 
during  the  year.  It  will  be  seen  from  the  above,  that  we  should  have 
five  eclijises  of  the  sun,  and  two  total  eclijises  of  the  moon,  during  the 
year,  which  is  the  gri'atest  number  that  can  jiossibly  take  jilace  in  a 
year.  Seven  eclijises  in  a year  do  not  occur  twice  in  a hundred 
years,  although  jierhaps  we  may  have  seven  (‘clijisc.s  in  one*  year’s 
time,  fill-  several  times  during  a century.  J'o  have  seven  eclijises  dur- 
ing the,  same  year,  it  is  necessary  that  the  moon  and  nodes  be  in  a 
particular  jiosition  on  the  first  day  of  January. 

After  the  sun,  moon  and  nodes  have  lieen  once  in,a  line  of  conjunc- 
tion ; they  return  nearly  to  the  same  position  again  in  22-3  lunations  or 
18  years  11  days  7 hours  43  minutes  20  seconds,  when  four  leap  years 
are  included,  or  one  day  less,  when  five  leap  years  are  included  ; con- 
seijuently,  if  to  the  mean  time  of  any  eclijise  of  the  sun  or  moon,  we 
add  18  years  11  days  7 hours  43  minutes  20  seconds,  we  shall  have 
the  mean  time  of  the  return  of  the  same  eclipse  for  a long  period  of 
time.  This  period  was  first  discovered  by  the  Chaldeans,  by  a long 
series  of  observations,  extending  through  many  centuries,  and  by  it 
they  were  able  to  foretell,  with  considerable  exactness,  the  appearance 
of  an  eclipse,  varying  at  most  but  a few  hours.  Every  eclipse  within 
this  period  of  18  years,  belongs  to  a separate  series  of  eclipses,  that  is, 
there  is  but  one  eclipse  during  the  18  years,  which  belongs  to  the  same 
series.  If  any  series  of  eclijises  commence  at  the  ascending  node,  the 
.shadow  of  the  moon  just  touehes  the  earth  at  the  north  pole;  at  the 
next  return  in  18  years,  the  shadow  will  pass  across  the  earth  a little 
more  to  the,  south,  and  at  each  return,  the  shadow  will  continue  to  jiass 
more  to  the  south  until  it  will  hjw'e  ajijieared  about  77  times,  which 
will  take  about  1,388  years,  when  it  will  jiass  oft’ the  earth  at  the  south 
jiole,  and  at  the  exjiiration  of  12,492  years,  the  same  eclijises  will  com- 
mence again  to  go  through  a similar  course.  Those  eclijises  of  the 
sun  whieh  come  in  at  the  descending  node,  the  shadow  of  the  moon 
first  touches  the  earth  at  the.  south  jiole,  and  at  each  return  jiasses  more 
lo  the  north,  and  finally  leaves  the  earth  at  the  north  jiole,  alter  having 
ajijieared  the  usiurl  number  of  limes.  'Fhe  velocity  ol  the  moon’s 
shadow  across  the  earth  in  Jin  eclijise  of  the  sun  is  about  l.B'iO  miles 
an  hour,  or  jibout  four  time.s  the  velocity  of  a cannon  ball.  The  moon 
xvhen  totally  eelijisi'd,  is  geiu'railv  visible,  if  it  is  above  the  horizon, 
and  the  sky  is  clear  : it  generally  ajijiears  of  a iiiint  dusky  red.  or 
eojijier  color,  this  is  caused  by  the  rjiys  of  tlu'  sun,  which  jiass  through 
the.  ill iiiosjihere  of  lh(‘  earth,  jind  iiri*  refracted  or  bent  inward,  so 
that  some  of  the  rays  fall  iijion  Ihe  moon  and  render  it  visible. 


^tUMvr  jkvt 

Nns  iMi  dO  ■gsjnoi  Ny*,i 


4^  AN.fCUPSE  ar  TML  SUN 


4G  I L T.  U S T R A 'I'  1-:  D 


LESSON  XLI. 

TIDES. 

Qxiestion.  What  motion  have  the  earth  and  moon,  besides  revolving 
around  the  sun  ? 

t Answer.  They  revolve  around  their  common  centre 
j of  gravity  ? 

i Q.  In  what  part  of  a straight  lino  joining  their  centres,  is  the  centre 
I of  gravity  situated  ? 

I A.  About  3,200  miles  from  the  centre  of  the  earth. 

I 

j Q.  What  effect  has  the  centrifugal  force  upon  the  water  on  the  oppo- 
! site  side  of  the  earth  from  the  moon  ? 

A.  It  causes  it  to  recede  from  the  centre  of  gravity, 
and  to  rise  on  that  part  of  the  earth. 

Q.  What  effect  has  this  upon  the  shape  of  the  earth  ? 

A.  Its  diameter  is  lengthened  in  the  line  of  the  moon’s 
attraction,  and  shortened  at  right  angles  to  it. 

Q.  What  tends  to  increase  this  oval  shape  of  the  earth  ? 

A.  The  inequality  of  the  attraction  of  the  moon  at  the 
different  sides  of  the  earth. 

[The  water  upon  the  side  of  the  earth  nearest  to  the  moon,  is  more 
attracted  than  the  centre  of  the  earth  ; the  water  upon  the  opposite  side 
is  less  attracted.] 

Q.  What  effect  does  the  turning  of  the  earth,  from  west  to  east  on  its 
axis,  produce  ? 

A.  It  causes  these  elevations,  or  tide  waves,  to  pass 
from  east  to  west  around  the  earth. 

Q.  What  is  tide  ? 

A.  It  is  the  rising  and  falling  of  the  waters  of  the 
ocean. 

Q.  How  are  the  tides  divided  with  respect  to  the  rising  and  falling 
of  the  water  ? 

A.  Into  flood  and  ebb. 

Q.  What  is  flood  tide  ? 

A.  It  is  the  rising  of  the  water. 

Q.  What  term  designates  the  greatest  elevation  of  the  flood  tide  ? 

A.  High  water. 

Q.  What  is  ebb  tide  ? 

A.  It  is  the  falling  of  the  water. 

Q.  How  often  do  flood  and  ebb  tide  occur? 

A.  Twice  in  about  25  hours. 

Q.  Do  the  tides  rise  at  the  stime  hour  every  day  ? 

A.  They  rise  about  an  hour  later  each  day. 

Q.  Why  do  the  tides  rise  later  ? 

A.  Ilecause  the  moon  passes  the  meridian  about  an 
hour  later  each  day. 

What  causes  the  moon  to  be  later  at  the  meridian  ? 

A.  It  is  ctiused  by  its  revolving  monthly  around  the 
earth  from  west  to  east. 

Does  the  attraction  of  the  sun  produce  an  effect  similar  to  that  of 
the  moon  ? 

A.  It  tends  to  raise  a tide  two  fifths  as  high. 

When  the  sun  and  moon  are  on  the  same  or  ojiposite  sides  of  the 
earth,  what  is  the  efliict  of  their  attractive  forces? 

I I A.  'I'hey  raise  a tide  etjutil  to  the  sum  of  their  separ- 
1.  tile,  tides. 

When  they  are,  in  (juiulrature,  whiit  is  the  eflect  of  their  counter- 
acting ? 

A.  'I'hey  rtiistt  a title  etjtial  to  tht;  diflerenco  of  their 
(ides. 

e-  - — 


A S T R O N O M Y | 

LESSON  XLII. 

Q.  How  are  tides  divided  with  respect  to  their  comparative  height? 

A.  Into  spring  and  neap. 

Q.  What  is  spring  tide  ? 

A.  It  is  the  greatest  flood  and  ebb  tide. 

Q.  What  is  neap  tide  ? 

A.  It  is  the  least  flood  and  eltb  tide. 

Q,  What  proportion  do  these  tides  bear  to  each  other? 

A.  The  neap  tide  is  about  three  sevenths  as  great  as 
the  spring  tide. 

Q.  When  do  spring  tides  occur? 

A.  Twice  in  each  hmar  month,  at  new  and  full  moon. 

Q.  When  do  neap  tides  occur? 

A.  Twice  in  each  lunar  month  at  the  qtiarters. 

Q.  What  effect  have  the  continents  upon  the  tide  waves  when  pass- 
ing round  the  earth  ?- 

A.  They  subject  them  to  great  irregularities. 

Q.  Which  side  of  the  continents  have  the  highest  tides,  the  eastern  [ 
or  the  western  ? j 

A.  The  eastern  side. 

Q.  Does  the  water  remain  permanently  higher  on  the  east  than  on  ^ 
the  west  side  of  the  continents  ? 

A.  The  gulf  of  Mexico  is  20  feet  higher  than  the 
Pacific  ocean,  and  the  Red  sea  is  30  feet  higher  than 
the  Mediterranean. 

Q.  Where  the  tide  wave  is  least  obstructed,  as  in  the  Pacific  ocean,  i 
how  much  behind  the  moon  is  it  ? I 

A.  It  is  two  or  three  hours  behind  it.  j 

Q.  How  long  after  the  moon  passes  the  meridian,  is  it  high  water  at  ; 
New  York  ? 

A.  About  82  hours. 

Q.  If  the  earth  were  uniformly  covered  with  water,  how  high  would 
the  tide  rise  ? 

A.  Not  more  than  two  or  three  feet.  (The  tide  at 
the  small  islands  in  the  Pacific  ocean  is  usually  less.) 

Q.  What  produces  the  greatest  eflect  in  causing  high  tides  ? 

A.  The  shape  of  the  land,  and  the  position  of  the 
shores.  I 

I 

Q,  Where  are  the  highest  tides  in  the  world?  > j 

A.  In  the  bay  of  Fundy.  | 

Q.  What,  besides  the  position  of  the  shores,  tends  to  raise  a high  [ 
tide  at  this  place  ? 

A.  The  meeting  of  the  tide  wave  from  the  North 
Atlantic  ocean,  with  the  main  one  from  the  South 
Atlantic. 

Q.  How  high  are  the  average  spring  tides  at  Cumberland  near  the 
head  of  the  bay  of  Fundy  ? 

A.  About  71  feet. 

Q.  How  high  are  they  at  Boston  ? 

A.  About  11  feet. 

Q.  At  New  York  ? 

A.  About  5 feet. 

Q.  At  Charleston,  South  Carolina. 

A.  About  6 feet. 

Q.  When  do  wo  have  the  highest  tides  in  the  northern  hemis- 
phere ? 

A.  At  new  moon  in  the  summer,  and  at  full  moon  in 
(he  winter.  (See  Diagram.) 


48  I L L U S T 11  A T M D 

LESSON  XL  III. 

ORBITS  OF  THE  PLANETS  AND  COMETS. 

Question.  What  is  the  orbit  of  a pritiiary  planet  ? 

Answer.  It  is  the  path  in  wliich  it  revolves  around 
the  sun. 

Q.  What  is  the  orbit  of  a secondary  planet? 

A.  It  is  the  path  in  whicli  it  revolves  around  its 
primary. 

Q.  What  is  the  form  of  the  orbits  of  all  the  planets  ? 

A.  Elliptical,  or  longer  one  Avay  than  the  other. 

Q.  Are  all  the  orbits  ellii)tical  in  the  same  proportion  ? 

A.  They  are  not ; some  are  more  elongated  than 
others. 

Q.  What  is  the  position  of  the  orbits  of  all  the  planets  ? 

A.  They  extend  from  west  to  east  in  the  heavens. 

Q.  Do  the  planes  of  their  orbits,  intersect  the  ecliptic  or  orbit  of 
the  earth  ? 

A.  They  do,  at  small  angles.  (See  Diagram.) 

Q.  Do  they  all  intersect  the  plane  of  the  earth’s  orbit  at  one  point, 
as  represented  in  the  diagram  ? 

A.  They  do  not ; but  intersect  it  at  dilTerent  points. 

Q.  Through  what  point  does  the  plane  of  the  orbit,  of  every  primary 
planet  and  comet  in  the  solar  system,  pass  1 

A.  Through  the  centre  of  the  sun. 

Q.  Are  the  planets  at  nearly  the  same  distance  from  the  sun  ? 

A.  They  are  not,  but  at  very  different  distances. 

Q.  Are  their  orbits  all  contained  within  the  zodiac  ? 

A.  They  are,  except  those  of  a part  of  the  asteroids. 

Q.  How  wide  is  the  zodiac  ? 

A.  Sixteen  degrees  wide  : eight  degrees  on  each  side 
of  the  ecliptic. 

Q.  Do  all  the  planets  revolve  around  the  sun  in  the  same  direction  ? 

A.  They  do ; ffom  west  to  east. 

Q.  Do  they  all  move  with  the  same  velocity  ? 

A.  The  velocity  decreases  as  the  distance  from  the 
sun  increases. 

Q.  Which  planet  moves  in  its  orbit  with  the  greatest  velocity  ? 

A.  Mercury. 

Q.  Which  moves  with  the  least  ? 

A.  Leverrier,  or  Neptune. 

Q.  When  docs  a planet  have  north  latitude  ? 

A.  When  it  is  above,  or  north  of  the  earth’s  orbit. 

Q.  When  does  a planet  have  south  latitude  ? 

A.  When  it  is  below,  or  south  of  the  earth’s  orbit. 


LESSON  XLIV. 

COMETS. 

Question.  What  arc  comets  ? 

Ansvwr.  'rh(!y  tire  l)odies  which  revolve  around  the 
sun  in  very  (dongalcd  oiljils. 

< How  are,  eomel;  ii'-ually  dislinguished  from  the  planets  ? 

A.  I'y  a luminous  train  or  ttiil,  on  tln^  ojtposite  side 
from  (In;  sun. 

f t.  I ihii,  hmiinom:  (rain  always  on  the  op[)OHite  side  from  the  sun  7 

A.  Not  aluiiys;  alow  have  b(;<‘n  observed  to  have 
a differoni  direction. 


A S r R ()  N ()  iVI  Y . 


Q.  Do  comets  ever  appear  willioiit  a luminous  train? 

A.  Some  iirc  entirely  destitute  of  any  such  iippernhige. 

Q.  ^Vhat  is  the  numl>er  of  comets  ? 

A.  'I'he  number  is  not  known;  tibont  5(K)  luive  been 
seen  .at  different  times. 

Arc  conn^ts  solid  Imdies  like  the  jdanets  ? 

A.  I'hey  generidly  tire  not;  all  hough  some  have;  been 
observed  to  have  a tiensc  nucleus,  or  head 

What  is  the  nature  of  comets  ? 

A.  They  are  sttjtposed  to  be  gaseous  tnatter,  in  the 
form  of  smoke,  fog,  or  c louds. 

Do  comets  shine  by  their  own,  or  by  refliicttMl  light? 

A.  They  shine  by  rellectcil  light. 

Q.  Do  they  all,  like  the  ])lanets,  revolve  in  the  same  direction  around 
the  sun  ? 

A.  They  do  not;  they  revolve  in  different  directions. 

Q.  Are  all  their  orbits  within  the  zodiac? 

A.  They  are  not;  their  orbits  tire  in  all  directions  in 
the  heavens. 

Q.  IIow  do  many  of  them  move  when  first  seen  ? 

A.  They  appear  to  move  in  almost  a direct  line 
towards  the  sun. 

Q.  Does  their  velocity  increase  as  they  aproach  the  sun  ? 

A.  It  does;  and  when  near  it,  they  move  with  im- 
mense velocity. 

Q.  IIow  fast  has  a comet  been  known  to  move  ? 

A.  880,000  miles  an  hour. 


Comets. 

Comets  were  anciently  viewed  by  mankind  with  astonishment  and 
fear,  as  being  forerunners  of  dreadful  calamities,  such  as  war,  flirnine, 
or  pestilence.  Many  ancient  philosophers  considered  them  as  only 
meteors  in  the  atmosphere.  Tycho  Brahe  was  the  first  who  showed 
that  they  belonged  to  the  planetary  system,  and  revolved  around  the 
sun.  The  orbits  of  all  the  comets  are  very  elliptical,  so  that  they 
approach  the  sun  almost  in  a direct  line,  and  after  being  involved  in  the 
light  of  the  sun  for  a short  time,  depart  from  our  solar  system  in  nearly 
the  same  direction,  in  which  they  approached,  and  remain  for  years, 
or  even  centuries,  beyond  the  limit  of  the  best  telescopes. 

Very  little  is  known  of  the  'physical  nature  of  comets;  the  smaller 
comets,  such  as  are  risible  only  with  telescopes,  generally  have  no 
appearance  of  a tail,  and  appear  like  round  or  somewhat  oval,  va- 
porous masses,  more  dense  towards  the  centre ; yet  they  have  no 
distinct  nucleus  or  solid  body.  Stars  of  the  smallest  magnitude  are 
seen  through  the  most  dense  parts  of  these  bodies.  It  is  very  probable 
that  the  luminous  part  of  a comet  is  something  of  the  nature  of  smoke, 
fog,  or  other  gaseous  matter.  Halley’s  comet,  which  appeared  in 
1456,  with  a tail  60  degrees  in  length,  and  spread  out  like  a fan,  has 
appeared  periodically  every  77th  year,  viz  : 1682,  1759,  and  in  1836  ; 
but  it  has  exhibited  no  tail,  or  luminous  appendage,  since  1456.  The 
comet  which  appeared  371  years  before  Christ,  is  said  to  have  covered 
a third  part  of  the  visible  heavens.  A remarkable  comet  made  its 
appearance  43  years  before  Christ,  and  was  so  bright  as  to  be  visible 
in  the  day  time  ; it  was  sui)poscd,  by  the  superstitious,  to  be  the  ghost 
of  Catsar,  who  had  just  been  assassinated.  The  following  are  some 
of  the  most  remarkable  comets  ; — 

Comet  of  1680,  length  of  the  tail  123,000,000  miles. 


Do. 

1744, 

u 

35,000,000 

Do. 

1769, 

U 

u 

48,000,000 

(4 

Do. 

1811, 

u 

130,000,000 

“ 

Do. 

181.3, 

u 

u 

130,000.000 

“ ' 

*9 


50 


I L I.  1)  S 'I'  U A '1'  i;  1)  A S T 11  <)  !\  <)  ,\I  Y 


COMETS  .—Continued, 


Qucslion.  WiiAT  are  tlio  principal  parts  of  a comet? 

Answer.  The  Nucleus,  the  iMivelope  aiul  the  I'iiil. 

Q.  ^\'hat  is  tlie  Nucleus? 

I A.  It  is  tlie  most  dense  or  solid  porlion,  somelhnes 
I called  the  head,  (See  the  comet  of  371.) 

I Q.  Wliat  is  the  Envelope? 

A.  It  is  a luminous  mat  ter  surrounding  the  Nucleus. 

! Q.  What  is  the  'J'ail  of  of  a comet  ? 

I A.  It  is  a long  lumiuotis  train  extending  off  from 
! the  head  in  the  opposite  direction  I'rom  the  sun.  (See 
j Note  1.) 

j Q.  tVhat  effect  has  the  eccentricity  of  their  oihits  ujion  the  motion 
I of  the  comets  ? (See  Note  2.) 

A.  Their  motion  increases  as  they  apjtroach  the 
sun  and  decreases  as  they  recede  from  the  sun. 

Q.  What  effect  has  the  change  of  position  u|)on  their  appearance  ? 

A.  Their  tails  iisiudly  increase  both  in  length  and 
breadth  as  they  approach  the  sun  and  contract  as 
they  recede  from  the  sun. 

Q.  Is  any  thing  known  of  their  Temperature  7 

A.  They  must  be  Aery  hot  \Adien  near  the  sun. 
(See  Note  3.) 

Q.  What  can  you  say  of  the  size  of  comets  ? 

A.  Their  Nuclei  or  heads  are  usually  small,  being 
only  from  33  to  2000  miles  in  diameter. 

Q.  Do  all  the  comets  revolve  around  the  Sun  continually  ? 

A.  Professor  Nichol  and  Sir  Joh.n  Ilerschel  are  of 
opinion  that  the  greater  number  Ausit  our  System  but 
once,  and  then  lly  olT  in  nearly  straight  lines  till  they 
pass  the  center  of  attraction  bet\A’een  the  Solar  System 
and  I'ixed  Stars,  and  go  to  reAmlve  around  suns  in  the 
far  distant  hetivens. 

Q.  How  were  comets  regarded  hy  the  ancients? 

A.  As  harhingers  of  famine,  pestilence,  AAmr  and 
other  dire  calamities.  (Note  4.) 

Q.  W hat  other  fears  have  been  entertained  of  comets? 

A.  'J'htit  they  might  come  in  collision  AAuth  our 
glohe  iuid  (hish  it  to  j)ieces  or  hum  every  thing  from 
i its  surfice, 

Q.  I - there  really  any  danger  of  a com(.‘t  striking  the  Earth  ? 

yl.  It  hits  heen  del(‘rmined  upon  mtil heiuittical  cal- 
cirlalions  that  there  is  not  mor(“  (Inin  I in  28  1 ,000,f)()0 
oj  chances  lor  a comet  to  strikt;  ihe  Miirth. 

Q.  \\'liat  M onhl  he  the  efficl  if  ;i  comet  slioidd  strike  Ihe  I larth  ? 

A.  '1  In-  only  eflccl,  it  would  produce,  is  llial  it 
miaht  iidu  <•  :i  ga -eons  mtider  itilo  our  afmosplu're 
which  iriighl.  |)|-oducc  disease  or  dcalli.  (Note  b.) 

I (J.  V\  lial  I l(no\\’n  ol  tlje  I’eriodic  tinici  of  comets? 

I'  A.  4 fo  1(^011111011  o(  only  (our  has  heen  delerniin- 

(•(1.  I I a.c  k > c'uuet , 3 year  ; I lida’s  comet , d i years; 
llallev’s  comet,  /d  \ears;  ('oiiiet  oi  Idst),  .diO  years. 


NOTES. 

Noth  1. — Cnnirla  assumr  n crciit  varifly  of  almja  H ; Rome  npiiRarlnr'  tile’  'ui  enor- 
mous fail,  oIIuth  like  n loiU’  swont  or  siilnc  ; liiil  nil  riitVi  d more  or  N nml  roiicave 
triwiirds  Itm  rofrions  liom  wliicti  llioy  come.  'J'lic  (yiinrl  of  1711,  ri’|>r,M.-ijl,',l  on  ll,,' 
o|i|M)Hil,'  pace,  c.M’ili'd  sicat  ain-ntion. 

Non;  2. — 'i'lio  orbits  of  ConiclM  aro  vary  clonc.al'  d,  liavinv  do  ir  ju l ilirlhm  very  near 
tlm  .‘'1111  ; (fi'o  di  loraiii,  pai;,-  l.'i,)  consi-ijiii  nlly  a;  tlii-y  appioarli  lli,.'  Sun  llc  ir  looiiy 
iricroasi’s  rapidly  liy  llio  iiicrcasi'd  iilliat'lioii  of  the  Sini,  mid  wlmii  at  llii'ii  j'nilulioii 
llioy  iiiovo  with  iiiimeiisc  vidocity. 

.XoiK  a. — 'I’lio  (ainioi  of  Ki.'S),  camo  witliin  ino.lotl  tiiilos  of  tli,-  ,,,i  iii<l  loo't  liavo 
rocoiv,  d 2S.0(M)  limoo  nioro  liulil  and  boat  tlian  llio  oailli  roroiv  il,,-  .‘■tin.  Sir 

Isaac  Newton  calcidalod  tlio  liont  o|  this  ('tniiot  to  ho  2.1)1)11  lino  ■ ".o.ilor  than  rnt  hat 
i/iiti,  and  that  il  would  roqniro  2,()()0  years  to  cool  ; ho  iii-sninod  that  the  Coniol  was  a 
solid  body,  whioli  was  not  llio  /nrC  It  is  a conorally  cono'  dod  fart  ai  the  pros,  nl  ilay 
that  the  rays  of  llio  Siin  to  jirodiico  mneh  lioal.  must  coiiio  in  contact  with  .-olid  hodios  ; i 
mill  as  Comets  are  of  an  oxlromoly  lliiii  oat-oon.'.  manor  llic  ray.  of  the  .■‘nn  may  pos  . 
thionf;li  them  withoni  jirodnciii!’ mncli  boat,  lliis  is  iiiorr  probably  llio  oa  o.  A\'o  lliid 
in  lu-condim;  liiKb  moiiiilains  that  the  iilmospboro  bocono  s very  cold  wbicb  on.'.dit  not  | 
to  bo  Ihe  case  if  the  rays  of  the  Sun  impart  mncli  lio.it  to  the  aimO'plicro  in  llo-ir  p.o-aoe  j 
ibronoli  it.  It  is  only  wlion  llo*  rays  of  the  Sun  coiio’  in  coniaoi  with  tlio  i arili  that 
mncli  boat  is  produced.  The  density  of  comols  is  probably  not  so  ('real  as  that  of  onr  | 
atyiO'|iberi!  and  as  they  have  no  solid  Nucloiis  or  lioiids,  the  jirobaliilily  is  that  com-  j 
paratively  very  little  boat  is  prodiieod  by  llieir  near  iipiiroaoli  to  ibo  .'S|iii.  | 

N'oi  k 4. — 'J'lic  Comet  of  ISll,  was  ro[;aidod  l>y  Ibo  ij.'norant  na  the  precursor  of  the  i 
fCiir  that  was  declared  in  the  following;  .sprino  beiwoon  Ureat  l;iilainmid  llio  Cnilod  | 
Stales.  In  somo  casos  Comols  have  excitoi]  fears  that  llic  ilay  of  jiidpiiiorii  was  at  band  1 
and  that  the  comot  was  sent  to  hum  up  ihe  varhl.  In  177:i,  .M.  I)olai  do  of  Ibiri.-  an-  I 
nOmiced  to  the  Academy  that  tliore  was  great  dantior  of  the  Com<-t  winch  was  soon  to 
appear,  striking  the  earth.  It  is  said  that  in  con.'oipn-nee  i.f  ibi.s  annoimcomont  wbon  i 
tlie  Comet  appeared,  many  persons  of  weak  minds  died  of  frii’ht.  1 

Note  5 — A Comet  by  striking  the  earth  would  produce  no  more  elb’ct  upon  the  j 
motions  of  the  earth  than  the  clouds  do  in  striking  against  Iiigh  moimtain.s  ; liosido.s  | 
onr  atmosphere  would  opiiose  a powerful  resistance,  being  more  dense  Ilian  tlie  comets, 
it  is  very  doubtful,  should  a Comet  strike  tlie  earth  that  it  would  penetrate  to  its  sur- 
face ; but  it  is  more  probable  tliat  it  would  he  retained  in  the  upper  portions  of  onr 
atmosphere.  It  is  very  probable  that  comets  contain  no  aqueous  vapors  ; but  arc  simply 
of  a gaseous  matter,  and  it  does  not  follow  from  this  that  it  would  produce  any  evil  con- 
sequences if  it  should  be  incorporated  with  our  atmosphere. 


HAS  THE  EARTH  PASSED  THROUGH  THE  TAILS  OF  COMETS? 

It  has  been  asserted  by  some  astronomers  that  the  Earth  has  on  several  occasions 
passed  through  the  Tail  of  a comet,  and  in  proof  of  this  fact  several  ca.ses  of  a singular 
or  peculiar  kind  of  Fng  have  been  noticed  at  several  periods.  The  first  of  which  any 
record  is  made  was  that  of  1783,  it  began  on  tlie  18th  of  June  and  at  places  very  re- 
mote from  each  other.  Ite.xtended  from  Africa  t<T  Sweden  and  thronghoiit  North  and 
South  America.  This  Fog  continued  more  than  a month.  It  did  not  appear  to  be  car- 
ried to  different  places  by  the  atmo.-ipliere  ; because  in  some  places  it  came  on  with  a 
north  wind  and  at  others  with  a south  or  east  wind,  it  prevailed  in  the  highest  summits  I 
of  the  Alps  as  well  as  in  the  lowest  valleys.  The  rains  which  were  very  abundant  in 
June  and  .Tuly  did  not  appear  to  disperse  it  in  the  least.  In  Languedoc  its  deii.sity  was 
so  great  that  the  Sun  did  not  become  visible  in  the  morning  till  it  was  twelve  degree.*! 
above  the  horizon  ; it  appeared  very  red  during  the  rest  of  the  day  and  might  be  looked 
at  with  the  naked  eye.  This  Fog  or  Smoke  hud  a disagreeable  smell  and  was  entirely 
destitute  of  any  moisture,  whereas  must  fogs  are  moist ; besides  all  this  there  was  one 
remarkable  quality  in  the  Fog  or  Smoke  of  1783,  it  ap[>eared  to  pos.se.ss  a phosphoric 
Iiro|ierty  or  a light  of  its  own  ; AA'e  find  by  the  accounts  of  some  observers,  that  it 
afforded  even  at  mid-riiglit  a light  equal  to  tliat  of  the  full  moon,  and  which  was  snfii- 
cient  to  enable  a person  to  see  objects  distinctly  at  a distance  of  two  hundred  yards, 
and  to  remove  all  doubts  as  to  the  source  of  this  light,  il  is  recorded  that  at  the  lime 
tliere  wa.s  a Neto  Moon. 

Another  remarkable  Fog  in  1831,  wliich  excited  the  public  mind  in  all  quarters  of 
lli,‘  globe,  repembled  so  mneh  that  of  1783,  that  the  description  given  of  it,  applies 
with  equal  force  to  that  of  1831. 

Nine  tel  us  took  iil  the  farts.  It  must  be  acknowledged  by  all  that  these  Fogs  origln- 
iilcil  from  some  uncommon  canse  ; now  the  next  question  is.  to  wbiit  causes  shiill  we 
iillribiile  the  /og.s  of  I7K3  and  1831.  Some  have  supposed  that  they  were  caused  by 
ii  iiiplion.s  of  Mount  ilerla  in  Iceland,  others  have  iidvanced  the  idea  that  an  immense 
Jire  hatl  in  |>euelraliug  our  almosplieie  was  there  but  partiiiily  ignited,  and  tliat  torrents 
of  smoke  were  (Ii  piKsiled  in  tlie  liiglier  regions  of  our  iilmospbere  and  finally  dilUiscd 
lliroiigli  it. 

These  explanations  are  very  unsalisfaelory.  If  tlie  Fogs  were  aelually  prodiieed  by 
the  eiii  lli’.s  passing  ibi'oiigli  liny  porlion  of  a roiiiel,  wc  have  no  cause  ol  fear  Irom  lliese 
boilles  wbicb  have  been  for  cciiliii'ics  a terror  ctrrnit  to  muiikinil  geiicraliy.  W'e 
will  eoiieeile  ib.'il  il  i.s  the  fuel  lliul  these  ['’og.s  were  priHliiccil  by  comets  mild  we  have 
II  lielii'r  expliiiiiilioii  of  llieir  i)rij;in. 


Si 


CNCKE'5  comet 


1 \.  I<  U S ']'  R A 'I'  i:  D A S 'r  l{  ()  N ()  AM  . | ■ 

. I 


L i:  S S O N X V . 

ATMOSPHERE. 

Question.  What  is  air? 

Answer.  It  is  an  clastic,  invisil)lc  lliiid,  Avliich  snr- 
roniuls  the  earth. 

Q.  Of  what,  liesidos  air,  is  tlio  atnios|)hf!ro  composed  ? 

A.  Of  vajtor,  carbonic  acid,  tind  other  ^iises. 

Q.  Is  the  atmosphere  of  tlio  same  dciisily  as  we  ascend  from  tlie 
earth  ? 

A.  It  "rows  thinner  or  less  dense.  . 

Q.  What  is  the  ostimatc'd  hielit  of  tlio  atmosphere? 

A.  About  forty-live  miles. 

Q.  AA'hat  is  the  pressure  ofttie  utinospliere  upon  the  earth? 

A.  Nearly  fifteen  jtonnds  to  the  s(|Uitre  inch.  (14.G.) 

Q.  AA'hat  is  ttie  weight  of  air  compared  with  water  ? 

A.  It  is  81 G times  lighter  than  wider. 

Q.  The  pressure  of  the  atmosphere  is  e(pial  to  a column  of  water, 
of  what  height  ? 

A.  Thirty-three  feet. 

Q.  Of  what  is  air  composed  ? 

A.  Of  oxygen  and  nitrogen  gases. 

Q.  In  what  proportions? 

A.  Twenty  parts  of  oxygen  to  eighty  parts  of  nitrogen. 


LESSON  XL  VI. 

REFRACTION. 

Question.  What  is  refraction  ? 

Answer.  It  is  the  deviation  of  the  rays  of  light  from  a 
straight  line. 

Q.  What  is  astronomical  refraction  ? 

A.  It  is  the  deviation  of  the  rays  of  light  in  tlieir 
passage  through  the  atmosphere. 

Q.  What  is  the  cause  of  this  refraction?' 

A.  It  is  caused  by  the  increase  of  the  density  of  the 
atmosphere  towards  the  earth. 

Q.  In  what  pait  of  the  heavens  is  the  light  of  a body  most  refj'acted  ? 

A.  In  the  horizon, 

Q.  Wlj^t  effect  does  this  refraction  have  upon  the  sun  at  its  rising 
and  setting  ? 

A.  It  makes  the  sun  appear  above  the  horizon  when 
it  is  actually  below  it.  (See  Diagram.) 

Q.  Does  this  afiect  the  length  of  the  day? 

A.  It  makes  the  day  froin  six  to  ten  minutes  longer, 
from  sun  rise  to  sun  set. 

f(?.  Is  the  light  of  a body  refraeted  when  it  is  in  the  zenith  ? 

A.  It  is  not.  (See  Diagram.) 

f-l.  What  is  twilight? 

A.  It  is  that  faint  light,  seen  before  the  sun  rises  and 
after  it  sets. 

Q.  What  is  the  cause  of  twilight  ? 

yj.  It  is  caused  by  the  atmosphere’s  reflecting  llie 
light  of  the  sun. 

(.J.  Twilight  ceases  when  the  sun  is,  how  far  below  the  horizon? 

A.  EighltMUi  degrtjes. 


I.ESSON  XL VII. 

PARALLAX. 

/ 

rhieslion.  \V'h\t  i'  parallax  ? 

Answer.  It  is  flu;  di(lcrence  between  the  apjtarenl 
and  trim  plar.e  of  a heavcidy  Itody. 


f^.  What  i.  ihe  apparent  place  of  a planet  ? 

yj.  It  is  (he  place  w here  it  appears  (o  be  ^len  seen 
from  (lu^  siirfaci'  of  the  earlh. 

(J.  What  is  (he  Irut'  place,  of  a planet? 

yl.  It  is  ( he  j)lae(‘  w here  it  would  apjtear  (o  lx*  if  seen 
from  (he  ceidrt;  of  (he  earlh,  or  renire  ol  motion. 

(J.  Where  i.s  ihe,  |)<'ir:ill:ix  of  a lifSTVonly  l>o(ly  tin*  ? 

yl.  At  (he  horizon,  and  (h'c.reases  (o  the  zenidi, 

(^>.  Ilo\T  a^^  |):irallaxr-s  divided? 

yl.  'J'hey  are  di\  idcd  into  two  kinds,  diurnal  and 
annual  jiarallax. 

(J.  What  i.s  diurnal  parallax  ? 

yl.  It  is  (In'  a|)parent  dillerence  in  (he  silualion  of  a 
lu'aveiily  body  when  semi  in  (he  zenilh  and  horizon 
o(  two  |)laces  at  the*  same  time.  (Sec;  parallax  of  Mars 
and  Moon.) 

Q.  What  is  annual  parallax  ? 

yl.  It  is  the  iipjiarenl.  dilTm’i'nce  in  (4ie  situalion  of  ti 
star  ;is  seen  from  (he  earth  in  opposite  points  of  its 
orbit, 

Q.  Have  iho  stars  been  observed  to  have,  any  sensible  parallax  ? 

yl.  A few  Inivc  been  ttbserved  tu  Inive  ti  simill  jitind- 
hi.x  of  a ptirt  of  a second.  (Non;. — No  [itindhix  has 
been  discovered  in  more  than  00  or  40  of  them.) 

Q.  A\  hat  is  the  cause  of  their  having  no  aj)preciablc  parallax  ? 

A.  Ilecause  they  are  tit  such  an  immenjje  distance 
from  us. 

Q.  If  the  earth’s  orbit  were  a solid  ring,  how  large  would  it  appear 
when  viewed  from  the  nearest  fixed  star  ? 

A.  No  larger  than  a lady’s  finger  ring. 

LESSON  XLVIII. 

LIGHT  AND  HEAT. 

Q.  What  bodies  produce  light  ? 

yl.  Luminous  bodies, 

Q.  Is  light  a substance  throxvn  off  from  a luminous  body,  or  is  it 
caused  by  a vibratory  motion  ? 

A.  It  is  probably  caused  by  the  undulations  of  an 
extremely  subtle  fluid. 

Q.  In  what  direction  are  the  rays  of  light  throxxTi  off  from  a luminous 
body  ? 

A.  In  straight  lines,  and  in  all  directions. 

Q.  With  what  velocity  does  light  move  ? 

A.  About  192  thousand  miles  a second.  (192,500.) 

Q.  How  xx*as  this  amazing  velocity  ascertained  ? 

A.  By  observing  the  eclipses  of  Jupiter’s  moons. 

Q.  In  what  proportion  do  the  light  and  heat  of  the  planets  increase 
or  decrease  ? 

yl.  In  inverse  proportion  to  the  squares  of  their  dis- 
tances from  the  sun. 

Q.  Which  planet  has  the  most  light  and  heat,  and  which  the  least  ? 

yl.  Mercury  has  the  most,  and  Leverrier  the  least. 

Q.  If  a board  a foot  square  be  placed  one  foot  from  a lightfH  candle, 
how  many  feet  square  would  the  shadow  be  upon  the  wall,  nine  feet 
from  Iho  candle  ? 

yl.  Niue  feet  square,  or  eighty-one  square  feet. 

Q.  What  amount  of  light  and  heat  would  fall  upon  the  one  foot  and 
U])on  the  8 1 feet  ? 

yl.  The  same  amount  of  light  and  heat  would  fall  upon 
each. 


( 


63 


VI  SI  B LC  HOR  t20N 


par  A VL  Ay, 


MB F' INACTION,,  PAMAliIiiAX„BI€}lIiT  & MAT' 


M 0 R N I N^c  _ 

- - — f rffAR  S ABOVE  TJ^E 


'X 
■i- 

A 

. o 

A 

-J. 

% 

evening. 

T M E SUN  .';rr.E.*?5.  i - - ' • 

VISIBLE  nOAiao^*  ' 


- WH  i nTt  rs'AauVLlY  BELOV/  .T. 


IT  IS  act'Jal'Ly  V£Low‘ 


' HORIZONTAL  PARALLAX  JOF  The  SUN  li 


THE  LIGHT  AND  HEAT  OF  THE  PLANETS  INCREASE  OR  DECREASE! 
IN  PROPORTION  TO  THE  SQUARE  OF  THEIR  D.ISTANCE5  FROM  THE 
SUN,  “ .■  , . ° . 


IF  THE  EARTH’S  ORBIT  WAS  A SOLID  RING  IT  WOUUD 


appear  no  larger  than  a LADY'S  finger  ring, when  SEEN  TROM 


THE  FIXED  STARS 


54  1 I.  L U S T II  A T E D 


L s s o N X I X . 

TERRESTRIAI.  AND  CELESTIAL  GLOBES. 

Question,  What  is  a ffloijo  ? 

Ailstver.  A globe  is  a roiiiul  body  or  sphere. 

Q,  How  many  kinds  of  globes  are  there.  ns(!(l  in  astronomy  ? 

A.  'Fwo;  terrestrial  and  celestiiil  globes. 

Q.  What  does  the  tcrn^strial  globe  re|)resent  ? 

A.  It  represents  tlie  earth. 

Q.  What  are  drawn  upon  tlie  .sindlice  of  the  terrestrial  globe? 

A.  Continents,  islands,  ntonnttiins,  oceans,  st'i'is,  rivers, 
republics,  kingdoms,  empires,  &c. 

Q.  What  does  the  celestial  globe  reprcvsent  ? 

A.  It  represents  the  heavens  as  seen  from  the  earth. 

Q.  What  are  usually  drawn  on  the  celestial  globe? 

A.  The  constellations  or  stars,  galaxy  or  milky  Avay, 
and  the  figures  of  various  animals  and  objects  frotn 
which  the  constellations  are  named. 

Q.  What  is  a constellation  ? 

A.  It  is  a group  of  stars,  to  which  is  applied  tlte  name 
of  some  animal  or  object. 

Q.  What  is  the  number  of  constellations  ? 

A.  Ninety-three. 

Q.  In  viewing  the  terrestrial  globe,  where  is  the  observer  supposed 
to  be  placed  ? 

A.  On  its  surfiice. 

Q.  In  viewing  the  celestial  globe,  where  must  the  observer  suppose 
himself  to  be  placed  ? 

A.  In  the  centre,  looking  towards  the  heavens.  (In- 
side looking  out.) 

Q.  What  is  the  galaxy  or  milky  way  ? 

yl.  It  is  a luminous  belt  forming  a complete  circle  in 
the  heavens. 

Q.  Of  what  is  the  galaxy  or  milky  way  composed  ? 

A.  It  is  a vast  number  of  stars,  so  liir  distant  from  us, 
and  situated  so  nearly  in  the  same  direction,  as  to 
appear  like  a thin  cloud. 

Q.  tV^hat  is  the  position  of  the  milky  way  in  the  heax’ens? 

A.  It  extends  from  northeast  to  southwest  through 
the  whole  circumference  of  the  heavens. 

Q.  What  are  the  celestial  pole.s  or  poles  of  the  heavens? 

A.  They  are  the  points  where  the  earth’s  axis,  if 
extended,  would  meet  the  heavens. 


LESSON  L. 

Qvrslion.  What  docs  the  plane  of  the  equator  form,  xvhen  extended 
to  the  heaven" ? 

Airnwr.  'I'he  equinoctial  or  celeslitil  equator. 

At  what  angl(!  do  the  cfdijjtic  and  equinoctial  intersect  each  other? 

A.  At  tin  angle  of  2‘Ia  degrees.  (2-‘T  28' ) 

Q.  What  does  the  [)lane  of  a meridian  foi'rn  when  extended  to  the 
hruiveti*^  ? 

' A.  A e.(de.stitil  meridian  or  circle  of  declination. 

! Q.  Vt'hat  are.  measurerl  on  ctde-tial  meriilians? 

! A.  Declination  and  itoltir  distance. 

I Q.  tV'hat  is  tin;  derdination  ofa  heaxamly  body? 

I A.  It  \'<  its  disttuiee  from  the  etpiinoctitil,  north  ttr  south. 

I Q.  'I'o  what  are  ihe  deidinniion  and  |)ol;ir  distance  always  etpial  ? 

A.  'I'licy  art;  etjiml  to  b(J  degretts,  or  ti  tptarter  of  a 
' tnrc.le. 

ty.  Xt'hnt  is  the  ritrlit  aseeiiHion  ofa  heavetdy  body? 

A.  It  is  its  di.".l:tmc  etisl  <»l  the  first  j)i>int  of  Aries 
1 irifiistinul  on  the  t tpiitiocl ial. 


A S T II  ()  N O I\I  Y . 


CJ,  What  angle,  expresses  the  right  ascension  ? 

A.  The  tingle  b(‘tv\een  the  meridian  pas.sing  through 
the  Itody,  iind  the  out'  passing  through  the  first  point  of 
Arit‘s. 

Q.  Mow  far  is  right  ascension  reetkoned  ? 

A.  3t)l)  degrees,  or  tpiite  round  the  heavens. 

What  an?  circles  of  lalitiiile  on  the  ccIcHtial  gloln?  ? 

A.  'I'lu'y  tire  grt'tit  circles  which  ptiss  throitgh  the 
})oles  of  t he  ecliptic,  and  cut  its  plam;  tit  right  angles. 

(/.  What  is  th(!  latitude  ofa  heavcidy  body? 

A.  It  is  its  distance  north  or  south  of  the  ecliptic, 
metisured  on  a circle  of  ct'lesl itil  latitude. 

VV'hat  is  the  Ituigiindc  of  a h(*aveidy  body? 

A.  It  is  its  disitmc.e  etist  of  the  first  point  of  Aries, 
measured  on  the  (‘clifitic. 

Q.  V\  hat  angle  expresses  the  longitude? 

A.  The  tingle  between  the  circle  of  hititude  passing 
through  t lie  body,  and  the  one  jiassing  througli  the  first 
jioint  of  Aries.  • 

(jl.  Where  is  this  angle  formed  ? 

A.  At  the  poles  of  the  ecliptic,  where  the  circles  of 
hititude  intersect  each  other. 

How  far  is  celestial  longitudi'  reckoned? 

A.  It  is  reckoned  300  degrees. 


LESSON  LI. 

Question.  Wh  at  is  a vertical  circle  ? 

A7isiver.  It  is^a  great  circle  in  the  heavens,  passing 
through  the  zenith  and  nadir,  and  cutting  the  horizon 
at  right  angles.  ■ 

Q.  What  vertical  circle  is  the  meridian  ? 

A.  It  is  tliat  vertical  circle  which  passes  through  tlie 
north  and  south  points  of  the  horizon. 

Q,  Which  is  the  prime  vertical  ? 

A.  The  vertical  circle  which  passes  through  the  east 
and  wxst  points  of  the  horizon. 

Q.  What  are  measured  on  the  vertical  circles  ? 

A,  Altitude  and  zenith  distance. 

Q.  What  is  the  zenith  distance  ofa  heavenly  body? 

A.  It  is  its  distance  from  the  zenith. 

Q.  'i’o  what  are  the  altitude  and  zenith  distance  always  equal  ? 

A.  They  are  equal  to  90  degrees. 

Q.  What  is  the  azimuth  of  a heavenly  body? 

A.  It  is  its  distance  east  or  west  of  the  meridian. 

Q.  What  angle  expresses  the  azimuth  ? 

A.  The  angle  between  tlie  meridian  and  the  vertical 
circle  passing  through  the  body. 

Q.  W hat  is  the  amplitude  ofa  heavenly  body? 

A.  It  i.^  its  distance  noilii  or  south  of  the  prime  vertical. 

Q,  What  angle  expresses  the  amplitude  ? 

A.  The  angle  betw^een  Ihe  prime  vertical,  and  the 
vertical  circle  passing  through  the  body. 

Q.  Where  are  the  angles  expressing  azimuth  and  amplitude  formed? 

A.  At  the  zenith  where  the  vertical  circles  inter.scct  i 
each  otlier.  { 

Q.  On  what  circle  are  these  angles  measured  ? 

A.  On  the  horizon.  , 

(,?.  'I’o  what  are  azimuth  and  amjilitude  always  equal  ^ f 

A.  'riiey  are  eqiitil  to  90  degrees.  | 

[The  diagram  can  1)0  used  to  illustrate  azimuth,  amplitude,  altitude,  I', 
and  /.('iiith  distance,  by  siippo.sing  the.  ('cliptic  to  repri'sont  the  celestial 
horizon,  and  (he  circles  of  ct?leslial  latitude,  to  riqu'esent  vertical  circles.]  j 


55 


I L L u s r R A T i:  das  'I'  r o n o m y . 


f'l’hr!  filiirs  iniicli  riirllicr  in  liin  (lircfiion  of  ihc  |,|;,,ic  of  lln* 

niillty  way,  lliaii  llicy  do  at  riglit  atiglcs  to  it.  .Si;i;  Dia(;kam.J 


Li:SS()N  I.TI. 

THE  FIXED  STARS. 

Question,  What  are  llioso  stars  callt’d  wl)icli  always  appf^ar  to  l)p 
in  the  same  situation  witli  resp(*ct  to  each  other? 

A/u^iver.  Tlioy  are  called  the  fixed  stars. 

Q.  AVhat  are  tlie  fixed  stars  supposed  to  he,  ? 

A.  They  are  sujtposed  to  he  suns  like  our  own,  with 
planets  revolving  around  them. 

Q,  Are  the  stars  liiniinons  or  o])ake  bodies  ? 

A.  They  are  luminous  bodies.  (Astronomers  have  no 
doubt  on  this  point.) 

Q.  Are  all  the  stars  of  the  same  magnitude  as  the  sun? 

*4.  They  are  not;  some  are  larger,  and  others  no 
I doubt  smaller  than  the  sun.  (Noti;.1.) 

[“From  tlie  orl>ital  motion  of  the  double  star  G1  Cygni,  compared 
with  its  distance,  Bessel  has  concluded  that  the  conjoint  mass  of  its  two 
individuals  is  ‘neither  much  more  nor  much  less  than  half  the  mass  of 
our  sun.’  From  the  photometric  ex[)eriments  of  Wollaston,  on  « (Al- 
pha)) LyriE,  compared  with  what  we  know  of  its  distance,  its  actual  emis- 
sion of  light  may  be  gathered  to  be  not  less  than  .'>2  times  that  of  the 
sun.  Sirius,  which  is  nine  times  as  bright  as  « byrm,  and  whose 
parallax  is  insensible,  cannot,  therefore,  be  estimated  at  less  than  100 
I suns.”  Edinburgh  Review.] 

j Q.  What  is  the  distance  of  the  nearest  fixed  star,  rt  (Alpha)  Centauri? 

j A.  It  is  so  far  distant  that  a cannon  ball  going  500 

' miles  an  hour,  would  take  four  millions  of  years  to 

I reach  it. 

' 

I ! Q.  W'hat  is  the  number  of  stars  whose  distance  is  imperfectly  known 
to  us  ? 

A.  About  35;  seven  of  which  have  their  distances 
determined  with  considerable  certainty. 

Q.  Do  all  the  stars  remain  of  the  same  brilliancy? 

A.  They  do  not;  some  exhibit  a periodical  change  in 
j their  light. 

i Q,  What  is  supposed  to  be  the  cause  of  this  change  in  their  light  ? 

I A.  The  revolution  on  their  axes  is  supposed  to  pre- 

j sent,  alternately  to  us,  sides  of  diflerent  brightness. 

j Q.  What  are  those  stars  called  which  appear  to  be  surrounded  by  a 
I thin  atmos|)here  ? 

I A.  Nei)ulous  stars. 

j Q.  Do  stars  ever  disappear,  or  new  ones  become  visi])le  ? 

A.  'I'hirteen  stars  hav'e  disappeared,  and  ten  new 
I ones  become  visible,  during  the  last  century.  (Note  2.) 

I (J.  tt’hat  is  supposed  to  be  the  cause  of  their  disappearance  ? 

I A.  'riiey  have  probtibly  ceased  to  be  luminous. 

j Q.  Mow  do  astronomers  account  for  the  appearance  of  new  stars? 

j A.  Opilke  bodies  mtiy  have  become  luminous,  or  new 
I suns  m:iy  have  been  created. 

I ^ 

LESSON  L 1 1 1 . 

fjurstion.  Wh  at  do  the  milky  way  and  the  single  stars  that  are  visi- 
j ble  to  the  naked  eye,  including  r»ur  sun,  constitute? 

I Aiisvtftr.  'I'hey  coiislitult;  tin  imtnense  cluster,  or  fir- 
mament, entirely  distinct  from  the  other  clusters  or 
nebitlat  of  the  hetivens.  (h'lt;.  1.) 

f What  is  the  sliapi!  of  this  grruit  cluster  or  firmament  ? 

A.  It  has  the  foriri  of  a wheel  or  biiriiing-ghtss. 


Q.  What  is  the  numlier  of  stars  in  fair  cluster’ 

A.  'I'liey  have  been  vtiriously  esliimiled  from  10  to 
100  millions. 

Q.  By  what  term  do  some  astronomers  designate  our  cluster  or 
firmaiuf'iil  ? 

yl.  'I'liey  call  it  the  univ  jrse.  (Noti;  .3.) 

Q.  Do  the  fixed  stars  have  any  apparent  motion? 

yl.  'I'liey  do,  but  it  is  .so  slight  as  not  to  be  easily 
detected. 

Q.  Around  what,  are  all  the  stars  in  our  cluster,  including  the  sun, 
supposed  to  revolve  ’ 

yl.  Arotind  Ih'^  common  centre  of  gravity  of  the 
cluster.  [Fig.  1.) 

Q.  Wha*  group  of  stars  is  thought  to  bo  near  the  centre  of  the 
cluster  ? . 

A.  The  Pleiades,  or  .seven  stars.  (Dr.  INIaedler.) 

Q.  In  what  part  of  the  cluster  is  the  solar  syslem  situated  ? 

yl.  It  is  comparatively  near  the  centre; 

Q.  How  far  from  us  is  the  centre  of  the  cluster  supposed  to  be? 

yl.  About  150  times  the  distance  of  the  nearest  fixed 
star. 

[I.ight  is  about  8 minutes  in  coming  from  the  sun  ; about  years 
in  coming  from  the  nearest  fixed  star,  « Centauri ; about  .500  years  in 
coming  from  the  supposed  centre  of  the  cluster;  and  about  5,000  years 
in  coming  from  the  most  remote  stars  in  the  cluster.] 

Q.  Ilfiw  long  will  it  take  the  sun  to  revolve  around  this  centre  of 
gravity  ? 

A.  About  twelve  millions  of  years. 

Q.  W’hat  other  motion  have  some  of  the  stars,  besides  around  the 
centre  of  the  cluster? 

yl.  Multiple  stars,  consisting  of  two  or  more,  revolve 
likewise  around  their  coitimon  centre  of  gravity. 

Q.  What  is  the  number  of  these  multiple  stars? 

A.  About  6,000  have  been  observed. 

Q.  Do  these  stars  appear  double  to  the  naked  eye  ? 

A.  They  do  not;  the  most,  require  a good  telescope 
to  separate  them. 

Q.  When  multiple  stars  consist  of  but  two,  what  are  they  usually 
called  ? 

A.  Double  stars,  or  binary  systems. 


Note  1. — Astronomers,  until  recently,  considered  all  the  stars  to  be  of  about  the  same  magni. 
tude.  and  probably  as  large  as  the  sun  ; and  that  tlie  stars  of  the  first  magnitude  owed  their  briF 
liancy  to  their  being  nearer  to  us  ; but  it  has  been  found  that  the  brightest  star  (Sirius)  in  the  whole 
heavens,  and  which  was  considered  to  be  the  nearest  fixed  star,  is  at  a much  greater  distance 
than  some  of  the  smaller  stars.  This  clearly  demonstrates  that  they  are  of  very  unequal  mag' 
nitude. 

Note  2. — There  are  now  seven  or  eight  well-attested  cases  of  fixed  stars  suddenly  glowing  for  a 
time  with  such  brilliancy  as  to  ho  visible  in  the  day  lime,  through  the  intensity  of  their  light ; then 
gradually  fading  away,  and  becoming  entirely  extinct.  Laflace  thinks  that  some  great  conilagra- 
tions,  produced  by  extraordinary  causes,  have  taken  place  on  their  surface. 

Note  3.— The  term  universe,  was  until  recently  used  to  denote  the  whole  creation  ol  God,  and 
was  never  used  in  the  plural  number : but  astronomers  use  tlie  term  to  denote  an  immense  fiiina* 
ment  or  cluster  of  stars,  entirely  distinct  from  other  clusters— of  which  there  are  many  thousands 
viMible  with  the  teloscopo— and  arc  at  un  immense  distance  from  each  other.  Honca  in  speaking 
of  thcio  clusters,  tlioy  call  lliem  univorflcs  — [Prok.  Mitchkm..) 


57 


DOUBLE 


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NORTH  STAR 


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fioli'ljl'K 


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Qlirsfhu.  WiiAT  appearance  lias  a nehiila? 

Aui^wer.  A iiehiila  n[)pears  like  a spot  of  pale 
seeJi  in  the  heavens. 

Q.  ()l  wliat  are  the  ik'IiiiIjc  composed  7 

A.  The  most  of  them  are  ,2:reat  clusters  of  stars,  so  far 
distant  as  to  appear  liktt  a thin  cloud. 

Q.  .\re,  there  many  of  lliein  ? 

A.  About  6,000  have  betm  discovered.  (Notu. --Their 
number  is  proba1)ly  much  greater;  jterhaps  infinite.) 

j Q.  What  is  the  distance  to  tliese  nehulie  ? 

I A.  Some  of  them  are  said  (o  be  so  far  disfant,  that 
j;  light,  traveling  192  thousnitd  miles  a second,  would 
i not  reach  us  in  less  than  30  millions  of  yeais.  [PKor. 
Mitchull.] 

Q.  Are  they  visible  to  the  naked  eye? 

A.  Only  a few  are  seen  without  a telescope. 

I Q.  How  laree.  do  they  appear  when  vii'wed  with  a telescope  ? 

I A.  Some  of  them  appear  as  large  :is  one  tenth  of  the 

{ disc  of  the  moon. 

I th  Are  these  nebulas  seen  in  all  parts  of  the  heavens? 

A.  They  are,  although  they  are  more  numerous  in  a 
j narrow  zone,  circumscribing  the  heavens,  at  right 
, angles  to  the  milky  way. 

Q.  Into  how  many  classes  may  nebiibe  be  divided? 

A.  Into  five  classes,  viz.,  resolved  nebula',  resolvable 
nebula;,  stellar  nebula*,  irresolvable  and  planefary 
nebula*. 

j (.).  What  are  resolved  nebulae  ? 

I A.  They  are  those  which  have  been  discovered  with 

; the  telescope  to  be  gi’eat  clusters  of  stars. 

Q.  What  are  resolvable  nebulae? 

A.  They  are  those  which  are  considered  to  be  com- 
posed of  stars,  but  are  so  far  distant  that  the  telescopes 
j liave  not  as  yet  resolved  them. 

1 What  are  stellar  nebulae? 

A.  They  tire  those  of  an  oval  or  round  shape,  increas- 
ing in  density  towards  the  centre.  (Note.- — They 
' sometimes  present  the  appearance  of  having  a dim  star 
in  the  centre.) 

What  are  irresolvable  nebuhe? 

A.  'riu'V  are  those  u iiich  are  considered  to  be  lumi- 
nous mttiter  in  an  afmospheric  stttfe,  condensing  into 
solid  bodies  like  the  stin  and  [)hinets. 

((t.  What  are  the  phimaary  mdmliB  ? 

>1.  'I’hvy  are  those  which  resemble  the  disc  of  a pla- 
lu't,  tind  are  considen'd  to  be  in  an  uncondensed  stiite. 

\ri-  all  nebuhe  beyond  our  cluster? 

A 'I’hey  tire,  extu'jit  the  milky  way,  and  nebulous 
sttirs. 

I’y  what  (general  term  do  astronomers  design.atc  each  nebula  or 

fdU't'T  ' 

A.  'I’hoy  call  ettc.h  nebuhi  a Umveuse,  or  PiKyiAiWENT. 

f/.  \t’lial  ean  you  say  of  the  great  nebula  in  tin;  (li'eyhounds  ? 

A.  It  ntsembles  our  own  cluster,  or  firmament  of 
stars. 

U'hat  r-.an  you  -av  of  the  great  nebulfi  in  OitioN  ? 

.^.'I’liis  ncbnhi  w;is  considered  to  be  luminous  mtit- 
h-r  in  an  uncttmb  nsfd  slate,  but  it  h.as  lafelv  been  dis- 
covered to  be  slar.s  by  I.ord  Kftsse,  with  his  powerful 


Uiiked  t'ye.) 

f,?.  Vt  hat  is  the  probable  cause  of  many  of  the  nebuhr  appearing 
elliptical  or  elongated  ? (.Si:k  Diaokam.) 

A.  It  is  probitltly  caused  Ity  the  (*dge  of  the  ncbnhi 
being  lurnt'd  more  or  less  towiirds  us. 

oiti(;i\  'i  iir,  SOI. A II  sYs’ri:.n. 

M*r>v  throriin  have  ticon  |iropomiili  il  at  illflcrrnt  nrrio.li  nf  tlia  hi.tor)’  of  Aatronmnv.  rr  >).»rtinK 
(lie  lormntitm  oI  oiir.Solur  S)«,leiu,  u«  wt  il  na  nil  oilier  ♦innii  nml  njutr-mii.  which  it  )in« 

pleased  the  i lt^  \t<iM  of  ai  i.  iiiiffi.n  to  rnll  into  existeni  r.  luit  no  our  Ima  t<nijied  •.!, 

favor  or  exntrd  no  violrnl  opposition,  asthr  theory  first  propo«ed  by  Sir  William  llenrhrl  irul 
liftei  warilK  more  e.speej.iHj  applied  h)  the  Cflebralcd  f.a  I'l.irir  to  the  lot  rntiltoii  of  the  «olar  -yttrin 
'I'll IS  tlionry  irtnj*  be  thus  Aalcd  : In  the  hej^unun'/  nil  (lie  inntlrr  compos jnj^  the  sim.  plniir*  ami 
xfttellitrs.  was  tlilhi^cul  throu(;h  apner,  in  n state  of  cxcocdingl)  minute  divnnoti  the  iiltimnte  parti- 
cles bring  hclil  a.stimlcr  b>  the  itptil-  on  ol  hent  Inpioresnof  iirnr,  nmler  Ihr  Rction  of  giiivjib. 
lion,  the  mass  asstinicd  h ri»iiud  or  globttlar  ihtipr.  ami  the  purtirle*  tembng  to  thr  erntrr  ol  gtavlly, 
a motion  ol  rotation  on  an  axis  would  commrnre  'I'hr  greal  mass,  now  Kratliially  cmjling  and  com 
(ien*ing  mn  1 increase  its  lot.uy  mot  on.  tlierrhy  Inerramng  thr  centnfngal  lorrr  at  Ihr  rqnator  of 
tlic  revolvini?  mass,  until,  finally,  a ring  of  matter  iti  actually  drlarhrd  liom  thr  e<|»inior.  amt  ii.  Irft 
revolving  in  apace  liy  the  Rlinnking  away  fioni  it,  of  tlic  interior  maiix  If  now  we  lollow-  thi«  i«o- 
late  ! ring  of  matter,  we  fnid  every  reason  to  helirve  that  its  particle^  will  gradually  coalencr  info  n 
globular  form,  and  in  turn  form  satell.tev,  ax  jt  was  lUcll  lormed  It  in  iintirrrAhur}  to  punuir  the 
reasoning  Initlier,  lor  llir  same  laws  which  Tuculuce  one  planet  ftom  the  ef|nator  of  the  reutral 
levoiving  mass,  may  produce  m my  until  fiiialiy.  the  procesx  in  ended  hy  a partial  sidiflification  of 
the  ceidral  masR,  no  groat,  that  gravity  aide«l  hy  tlir  attraction  of  coliexion.  ia  more  than  aufWeieiil 
to  re'^ist  the  ai’tion  ol  the  ccntcfugol  foic*-.  and  no  fnitlirri  lrnige  ocenra 

Il  has  been  urged  in  favor  of  thia  theory,  llial  it  necountx  for  the  Ntrikmg  prciiljaritir*:  which  are 
found  in  th(»  organivation  ol  the  aolar  system.  That  the  rings  of  Hatnrn  are  poxilivr  proofa  of  tho 
liutli  of  the  theory,  tliey  having  cooled  ami  < ondenseil  without  hreaking  Thai  Die  iudividiialx  con- 
stituting a system  tlius  [irodm-ed.  must  revolve  and  tolato  as  do  the  plnncts  and  xatrlhirs.  an<l  in 
orbits  ol  the  precise  figure  and  position,  as  tho'C  occupied  by  the  planets  It  accounts  for  the  rota- 
lion  ol  the  sun  on  it"  axis,  and  prc^ent8  a solution  of  the  strange  appeamnee  connected  w ith  the  euii 
called  the  /odiacal  Light  It  goes  fiirthei  and  accounts  for  the  formation  of  single,  dniihle.  arnl  i 
multiple  suns  and  sfars— and  by  tlic  remains  of  chaotic  matter  in  thr?  inteiKtices  between  the  stars, 
and  which  are  finally  drawn  to  some  particular  snn,  whose  iriHnencc  in  Die  end  prepondei alcsj 
accounts  for  the  comets  which  6nler  our  sj  stem  from  every  region  in  space  ' j 

in  support  ol  this  tlieory  it  has  tieer.  iirgoi!  tiiat  the  comets,  in  their  organization,  present  ns  with  I 
S]>ecim(*n"  of  thi.s  finely  divided  nebulous  or  chaotic*  matter — and  tliat  the  tele'^cojx*  reveals  clomly  j 
patclios  of  light  of  tmlofinitc  extent,  scattered  thronghonl  space,  which  give  evidence  of  being  yet  | 
unformed  and  chaotic.  'Lhat  many  stars  are  lound  in  which  tlie  bright  nucleus  or  centre  is  Mir-  [ 
rounded  hy  u halo  or  liaze  of  nebulous  light,  and  that  round  nehulons  bodies  are  sfM»fi  wifli  the  t»-l. 
escopc.  ol  an  extent  vastly  greater  tlian  would  fill  Die  entire  space  encircled  bv  the  enormous  orbit 
of  the  planet  La  Verricr,  or  having  a diameter  greater  than  7n00  millions  of  miles 

Such  aie  a few  of  tlic  arguments  in  support  of  this  ino^t  c.xtraordinary  theory  We  now  present 
the  objections  which  liave  beer,  most  stroiigly  insiste*!  on  'J'he  retrograde  motions  of  tlie  sytelldes 
ol  Herschel.  and  their  groat  inclination  to  Die  plane  of  the  ecliptic  cannot  he  accotintcd  for  by  this 
theory.  That  comjmtation  sliows  that  no  atmosphere  of  uncondon’Jed  nebulous  matter  can  extend 
to  so  great  a distance  from  the  sun,  as  docs  the  matter  composing  Die  Zodiacal  Idgiit.  and,  Anally, 
that  the  nebulous  matter  in  the  heavens  will  ultimately  he  re.solved  into  immense  congeries  and 
clusters  of  stars,  wliose  great  distance  has  hitherto  defied  the  power  of  the  best  inatriimems. 

In  reply  to  the  first  objeetjon.  the  friends  of  the  theory  doubt  the  lacts  with  reference  to  the  satel* 
lites  of  Ilerscliel  Tliey  reply  that  the  matter  composing  the  Zodiacal  Light,  being  in  the  nature 
of  cometary  matter,  is  thrown  to  a greater  distance  from  the  sun  than  gravity  would  warrant,  by  , 
that  power  residing  in  the  sun  w'hich  is  able  on  the  approach  of  comets  to  project  tho«e  enormous 
trains  of  light,  which  sometimes  render  tliern  so  wonderful.  As  to  the  last  objection,  it  is  urged 
that  although  many  nebulae  will  doubtless  be  resolved  into  stars,  by  u.sing  more  powerful  teles, 
copes,  yet  that  these  same  telescopes  will  reveal  more  new'  nebulae  which  cannot  be  resolved,  than 
they  will  resolve — and  as  to  the  existence  of  nebulous  matter,  it  is  perfectly  demonstrated  by  the  i 
physical  organization  of  comets,  and  the  existence  of  nebulous  stars.  , 

Such  w'as  the  state  of  the  Astronomical  argument,  when  Lord  Rosse’s  Great  Reflector  was  first  | 
applied  to  the  exploration  of  the  distant  regions  of  space.  In  a religioti.s  point  of  view,  thw  theory  » 
had  excited  no  small  amount  of  discussion,  ip  consequence  of  its  sujiposed  Atheistical  tendencies.  1 
The  friends  of  the  theory  contend  that  it  was  no  more  .Atheistical  to  admit  the  formation  of  the 
uniierse  by  law,  than  to  acknowledge  that  it  is  now  sustained  by  laws.  Indeed  since  w'e  must  go  , 
to  the  first  great  cause  for  matter  in  its  chaotic  state,  as  well  as  for  the  laws  which  govern  matter,  ! 
that  this  theory  gave  to  us  a grander  view  of  the  omniscience  and  omnipotence  of  ( jo«l  tlian  could  ■ 
be  obtained  from  any  other  source.  In  fine  that  it  harmonized  with  the  declaration  of  scripture,  t 
W'hich  tells  us  that  “ In  the  beginning  God  created  the  heavens  and  the  earth,  and  the  earth  was 
without  form  and  void^  If  the  earth  came  into  existence  in  its  pre.sent  condition,  then  it  had  //u?/i 
and  w'asno^  void.  Hence,  this  first  grand  declaration  of  the  inspired  writer  must  refer  to  the  forma- 
tion of  the  matter,  of  which  the  heavens  and  earth  were  afterwards  formed.  Some  went  so  far  as 
to  trace  out  dimly  a full  account  of  this  theory  in  the  order  of  creation,  as  laid  dow  n in  ( ienesis. 

Let  us  now  proceed  to  the  disco  veries  of  Lord  Rosse,  and  their  influence  on  this  greatly  disputed 
theory.  The  space  penetrating  power  of  his  six  feet  reflector  is  much  greater  than  that  of  Sir 
William  Herschel’s  great  teie.scope,  and  it  was  anticipated  that  many  nebula  w’hich  were  unre- 
resolved  into  clusters  of  stars  by  Herschel,  would  yield  under  Die  greater  power  and  light  of  Lord 
Rosse’s  telescope.  This  has  proved  to  be  the  fact.  Very  many  nebuljE  have  been  removed  from 
their  old  places,  and  must  hereafter  figure  among  the  clusters,  w'hile  we  are  informed  that  many 
yet  remain,  even  of  the  old  nebuhe,  w'hich  defy  the  power  of  the  monster  telescope. 

The  most  remarkable  object  which  has  been  resolved  by  Lord  Rosse.  is  the  great  nebula  in 
Orion,  one  of  the  most  extraordinary  objects  in  the  heavens.  (Skk  Diagram.)  Its  size  is  enormous, 
and  its  figure  very  extraordinary  In  certain  parts  adjoining  the  nebula  the  heavens  are  jet  black. 
either  from  contrast  or  by  the  vacuity  of  these  regions.  Two  immense  spurs  of  light  are  seen  to 
project  from  the  principal  mass  of  the  nebnia,  and  to  extend  to  a most  extraordinary  distance.  This 
will  be  better  understood,  by  remembering  that  at  tlie  distance  at  w’hich  this  nebula  is  removed 
from  us,  the  entire  diameter  of  the  earth’s  orbit.  190  millions  of  miles,  is  an  invisible  point,  less  than 
one  second,  while  tliis  nebula  extends  to  many  thou-sands  of  times  this  distance,  and  more  probably 
to  many  millions  of  times. 

Several  stars  have  been  found,  and  are  visible  on  the  nebula,  but  have  hitherto  been  regarded  as 
being  between  the  eye  of  the  observer  an*l  this  remote  object.  Sir  William  Herschel  was  unable 
to  resolve  this  mysterious  body,  and  yet  (he  nebula  gave  indications  of  being  of  the  resolvable 
kind,  by  its  irregular  and  curdled  appearance  under  high  ]>ow'ers.  Several  years  since  Dr.  J. 
Lamont.  of  Munich,  after  a rigid  setutiny  of  this  nebula  with  his  great  Refractor,  pronounced  a 
portion  of  it  to  he  composed  of  minute  fsfellar  points,  and  predicted  its  final  perfect  resoluiion  into 
stars  by  greater  jiower.  'I’his  jircdiction  has  been  fully  verified,  for  Lord  Rosse’s  great  Reflector 
huH  fiolVcd  tbc  mystery,  and  filled  tliis  extraordinary  object  with  the  “jewelry  of  stars  ” 

Rut  the  question  recurs,  what  have  the  defenders  of  the  nebular  theory  lost,  or  its  enemies 
giiiniMl  by  this  interesting  discovery  I We  arc  all  liable  to  reach  conclusion^  too  hastily,  and  to 
join  isNuo  on  Inlse  points  If  the  nebular  tlieory  dc]iende<l  for  its  existence  upon  the  irrc'-oUaliility 
of  the  nehulii  in  Orion,  then  indeed  has  the  theory  been  entirely  exploded.  But  this  i.s  not  the  fact 
No  one  has  nsNcrted  Unit  Dio  great  nebula  in  Orion  was  urbttlous  tuntfrr,  and  if  it  were  not,  Uicn 
none  existeil  Hnch  an  issne  w'ould  have  been  a false  one,  had  it  been  made. 

'Die  theory  has  neither  lost  nor  guinc<l  by  the  discoveries  thus  fur  made  ; what  time  may  devol- 
ope  il  is  jm])ossihle  to  say  In  case  cerluin  data  can  he  ohtiiinod,  which  ajipear  to  he  accessible. 
Dien  indoeil  niay  wo  deinonKlrnte  its  truth  or  falsehood,  by  mathematical  investigation  Until 
then,  the  safer  plan  is  neither  to  adopt  nor  roject.  but  investigate  until  absolute  truth  shall  rew’ard 
our  long  coutlnimd  Inlior.  and  reveal  Die  mvstery  of  Die  organization  of  that  stupendous  sy.stcm,  of 
which  our  huinble  planet  forms  an  insignificant  pert 


58 


LESSON  LIV. 

NEBULiE. 


I I.  L IJ  S T R A T !■:  D A H T R ()  N ()  M Y . 

telescope.  (Note. — 'I'liis  nebula  is  visible  to  the 


nebulae  or  CLUSTERS  of  STARS  at  an  IMMENSE  DISTANCE  BEYOND  OUR  CLUSTER  1 

I 


-7'his  has  lately  heeiL  chs cover'd  to  le 
l-y ZORD  jiosSE  with.  hisFowerfiilTele. 


}'lnnetar\’  J^^ehvlac- 


I iJTesolvable  and  Planetary  Nebula  e 

I 


EemaTkaLle  Nebulae 


Elongated  Nebulae 


D'unvbeZl 


A ebnVad  i)v  the^  Gi eyhounds 
7'h  i.v  ]V^ehv.Lae  t'esernbles  ouron'n  CluHn 


CO 


I L L II  « R A 'J'  E D A S R ()  N ()  M Y . 


DESCRIPTION  AND  USE  OE  THE  SIDEHEAL  MAPS. 


TirKSE  Maps  have  been  drawn  hy  the  Author  willi  ffreat  care,  in 
order  to  insure  perfi'ct  accuracy  in  tlieir  representations  of  the  heavens 
at  the  limes  specified  in  the  annexed  tallies.  'I'hiyy  liave  heen  con- 
structed to  show  the  sidereal  homi?pher(*  visildo  on  the  pai'alhd  of  lali- 
{ tnile  and  nn'ridian  of  New  York  (City.)  'I’o  insure  the  Greatest  anionnt 
I of  accuracy,  the.  stereographic  projection  has  lieen  made  use  of,  because 
j of  all  projections  that  occasions  the  least  possible  disarrangement  of  the 
I relative  positions'of  the  stars  and  the  angles  they  form  one  with  ano- 
j ther.  There  is  a difficulty  in  n'diiciiig  a concave  or  globular  surface  to 
i a plane  without  distortion  taking  place  somewhere  ; and  in  the  projec- 
tion hen;  adopted  a little  compression  will  be  found,  graflually  increasing 
from  the  horizon  to  the  centre  of  the  map.  'I'ho  constidlalions  near  the 
zenith  will  be  found  to  be  somexyhat  smaller,  and  the  stars  nearer 
together,  thati  xihen  near  the  edge  of  the  nia)  or  horizon.  Several 
stars  often  appear  in  the  heavens,  so  as  to  lb  ■ i a group,  presenting 
the  appearance  of  a triangle,  a rhomboid,  trapezium  or  parallelogram  ; 
these  figures  are  more  correctly  preserved  by  this  [irojection  than  by 
any  other  which  might  have  been  made  use  of.  'I'he  centre  of  each 
map  represents  the  zenith  on  the  parallel  of  New  York,  or  that  point 
in  the  heavens  directly  over  the  observer’s  h(*ad  at  the  time  spc'cified  in 
; the  annexed  tabh's.  They  xvill  answer  equally  well  fiir  any  jilace 

j within  the  United  States,  by  making  an  allowance  for  the  situation  of 

j ! the  place  north  or  south  of  the  parallel  of  New  A'ork.  For  instance,  to 
i an  observer  at  Washington  the  zenith,  as  represented  on  the  tnaps, 

xvould  be  aViont  Sg®  degrees  to  the  north  of  his  zenith  ; also,  to  an 
observer  at  New  Orueans  the  zenith  of  the  maps  would  be  about  12° 
I degrees  to  the  north  ; at  Quebec  the  zenith  of  the  maps  would  be  about 
j 6°  degrees  to  the  south  ; but  to  all  places  in  the  New  England,  Middle, 

! and  Western  States,  the  variation  would  be  so  small  that  it  would 
I hardly  be  perceptible,  unless  by  accurate  observation.  As  we  go  north 
{ or  south  our  sidereal  hemisphere  is  continually  changing.  If  we  go 
north  new  stars  seem  to  emerge  from  the  northern  horizon,  while  those 
near  the  southern  horizon  disappear  below  it ; anu  if  we  should  conti- 
nue our  journey  to  the  north  pole,  we  should  find  the  north  star  in  the 
zenith,  or  directly  over  head,  and  that  the  .stars  visible  to  us  did  not  rise 
nor  set,  but  described  circles  around  the  north  star  every  24  hours  ; 
these  circles  increasing  in  diameter,  according  to  the  distance  of  the 
star  from  the  north  star.  To  a person  thus  situated,  the  equator  would 
I be  in  the  horizon,  and  he  would  see  none  of  the  stars  in  the  southern 
I heriiijfdierc.  Ifthere  were  inhabitants  at  the  south  pole  they  would  be 
j sirriilarlv  situated  with  regard  to  the  stars  in  the  southern  hemisphere  ; 

' they  woidd  never  see  the  stars  on  the  north  side  of  the  equator  or  in  the 
northern  hemisjihere,  nor  would  the  stars  in  the  southern  hemisphere 
^ ever  set  to  them.  'Fo  the  inhabitants  at  the  equator,  the  whole  of  the 
I stars,  from  pole  to  [lole,  would  rise  and  set  pei-pendicularly  to  their  hori- 
I zoii  once  in  every  21  hours.  As  the  etpialor  has  no  latitude,  so  has 
I its  zenith  no  declination,  liecause  the  celestial  equator  is  directly  over 
I it  on  a line  from  east  to  west.  If  an  obse.rver  moves  towards  either 
I pole  fiom  the  equator,  for  every  degree  of  his  progress  his  zenith  will 
j ; have  just  HO  many  degrees  of  declination,  and  as  many  degrees  can  he 
' nee  beyond  the  pole  towards  which  he,  is  advancing  ; and  he  will  loS(*- 
I Hi^hl  of  ihe  pole  from  wliieh  he  is  reci-ding  in  the  same  |iroporti()n. 
I'lir  example,  aw  the  itdialiitantH  of  New  \’ork  are  situated  near  41" 
degree  iioftli  of  the  erpiator,  their  zenith  is  elevated  41"  dcgrei’S  above 
the  r’ele.tial  eipmtor  ; and  it  follows  that  the  iidiabitants  on  the  parnl- 


lei  of  New  York  can  see  all  the  stars  within  Ul"  degrees  south  of  the 
equator — for  4 I " arkled  to  4!)°  makes  f)0" — the  distance  from  the  zenith 
to  the  horizon  ; also  between  the  zenith  of  New’  York  and  the  north 
pole,  are  4il"  tiegrees  ; rerpuring  41"  degrees  beyond  the  pole  to  make 
up  th(x  comphummi  of  90  di’grees  ; conserpienlly  the  stars  41"  degrees 
b('yond  the  north  pole  never  set  to  the  inliabitanls  living  on  the  parallel 
of  New  ork,  but  de.scribe  circles,  or  appear  to  revolve  around  the  jiole 
star  every  24  hours. 

EXPLANATIONS,  SHOWING  THE  MANNER  OF 
USING  THE  MAPS. 

TitE  pupil  should  lie  particularly  instructed  in  the  manner  of  using 
these  map.s,  or  they  w'ill  be  inclined  to  u.se  them  in  tlie  .same  rnaniu’r 
as  they  do  the  maps  of  a Geography  or  .\tlas,  which  will  conflise  and 
confound  them.  In  using  a geogra[)hical  ma|)  the  pupil  is  instructed  to 
face  the  north,  and  lay  the  map  befon-  him;  then  the  top  lepresents  the 
north,  the  right  hand  east,  iVc.  : but  it  will  be  obsorved,  that  if  this 
mode  be  ado|)tefl  with  these  maps,  the  right  hand  represents  tin?  west 
and  the  left  hand  the  east.  Each  map  is  intended  to  rcpre.sent  the 
whole  visible  lieaxens  at  the  time  given  fiir  observation  ; hence,  if  we 
face  the  south,  anrl  liold  the  mafi  up  over  the  head,  with  the  pole  star 
directed  towards  the  north  star  in  the  heavens,  it  wull  then  represent 
nearly  the  condition  of  the  heavens.  In  viewing  the  stars  south  of  our 
zenith,  face  the  south,  and  hold  the  map  up  in  front  of  the  eve;  but  in 
viewing  the  stars  to  the  north  of  onr  zenith,  face  the  north,  turn  the 
map  bottom  iqnvards,  and  liold  it  so  that  the  pole  star  on  the  rnaf)  shall 
correspond  with  the  pole  star  in  the  heavens,  tlien  the  stars  on  the  map 
will  indicate  the  positions  of  the  .stars  in  the  heavens.  In  viewing  the 
stars  to  the  east,  face  the  east,  and  hold  the  map  up  befiire  the  eye,  with 
the  top  turned  towards  the  north  ; the  map  will  then  indicate  the  correct 
positions  of  the  stars  : also,  in  viewing  the  stars  to  the  west,  fiice  the 
west,  and  hold  the  map  up  befiire  the  eye,  with  the  top  turned  towards 
the  north.  Great  care  should  be  taken  when  an  observation  is  made, 
so  a.s  not  to  mistake  the  planets  Venus,  IMars,  or  Jujiiter,  for  fixed  stars. 


DIRECTIONS  FOR  FINDING  THE  NORTH  STAR, 
AT  ANY  TIME. 

Every  pupil  should  be  instructed  in  the  manner  of  pointing  out  the 
North  Star  at  any  time  of  the  night.  If  they  are  enabled  to  do  this  at 
any  time,  it  will  assist  them  in  making  other  important  observations,  as 
well  as  biMiig  of  use  on  many  occasions  which  occur  in  the  life  of  every 
man.  Many  persons  have  been  lost  in  a rRAiRii;  or  other  unfrequented 
places,  when  if  they  had  been  able  to  have  told  the  points  of  the  com- 
pass they  could  have  extricated  themselves  from  their  lost  situation. 
This  may  be  done  in  a very  easy  manner.  There  is  hardly  a child  of 
10  yeais  of  age  who  cannot  at  any  time  of  night  [loint  out  the  stars  in 
the  Gicat  Rear  xvhich  form  what  is  called  the  Gre.at  Diim’er.  Now 
if  an  imaginary  line  be  drawn  through  the  two  stars  which  form  the 
I'ront  edge  of  the  Dipper,  from  the  bottom  towards  the  top,  and  continued 
about  2tt"  degrees,  it  will  pass  very  near  the  North  Star — so  near  that 
it  cannot  be  mistaken,  there  Ixung  no  other  stars  of  that  magnitude 
near  it.  It  should  be  borne  in  mind  that  this  rule  holds  good  in  what-  I 
ever  position  the  I)ip|>er  may  be  at  the  time.  _ ij 


ILLUSTRATED  ASTRONOMY.  Gl 


PRINCIPAL  CONSTELLATIONS  VISIBLE,  FROM  JANUARY  21  TO  APRIL  17. 


Ursa  Major,  the  Great  Bear. — Tlie  first  seven  stars  in 
( this  constellation  form  what  is  called  the  Great  Dipper.  It  is  situated 
about  15  degrees  north  of  the  zenith,  and  a little  to  the  east  of  north. 
It  is  exactly  bottom  upwards,  with  the  handle  towards  the  east.  There 
I are  four  stars  which  form  the  dipper,  and  three  in  the  Tail  of  the  Bear, 
which  Ibrm  the  handle.  'I'hese  stars  cannot  fail  to  be  recognized  at  a 
glance.  Six  of  these  stars  are  of  the  second  and  one  of  the  third  mag- 
nitude. The  first  two,  «,  are  called  pointers,  as  a line  drawn 
through  them  towards  the  horizon  would  pass  very  near  the  North  Star, 
which  is  about  30  degrees  from  them  towards  the  horizon. 

Ursa  Minor,  the  Little  Bear. — The  stars  in  this  constella- 
tion form  a figure  called  by  some  a Wagon,  and  by  others  the  Little 
Dipj)er.  It  is  north  of  the  Great  Dipper  and  east  of  the  North  Star, 
which  is  in  the  end  of  the  handle.  The  North  Star  is  at  the  end  of  the 
tail  of  the  Little  Bear. 

Taurus,  the  Bull. — The  star  «,  or  Aldebaran,  is  one  of  the  first 
magnitude,  and  is  in  the  right  eye  of  the  Bull  ; hence,  it  is  sometimes 
called  the  Bull’s  Eye.  This  constellation  is  situated  nearly  west,  and 
about  20  degrees  above  the  horizon,  ■'fhe  cluster  of  stars  on  the  head 
of  the  Bull  is  called  the  Hyades.  There  is  a small  cluster  of  stars  on 
the  neck  of  the  Bull,  and  north  of  the  word  Taurus  on  the  map.  It 
consists  of  seven  stars,  very  near  together.  This  group  is  called  the 
Pleiades,  or  Seven  Stars.  Six  of  these  stars  only  are  visible  to  the 
naked  eye. 

Orion. — This  is'  one  of  the  most  remarkable  constellations  in  the 
heav'ens,  and  was  familiarly  known  to  the  ancient  writers,  Jon  and 
Homer.  It  contains  two  stars  of  the  first  magnitude,  Betelgeuse  on 
the  right  shoulder,  and  Rigkl  on  the  left  foot,  of  Orion.  Half  xvay 
between  these  two  stars  are  three  stars  in  the  girdle,  in  a right  line, 
forming  Jacob’s  Staff,  or  the  Three  Kings,  as  they  are  sometimes  called. 
There  is  a large  nebula  seen  in  this  constellation,  or  rather  through 
it,  as  the  nebula  is  at  an  immense  distance  beyond  the  stars.  Accord- 
ing to  fable  Orion  was  a mighty  hunter,  who  accompanied  Diana  and 
Latona  in  the  chase. 

Gemini,  the  Twins. — The  two  principal  stars  in  this  constella- 
tion are  («)  Castor  and  (pf)  Pollux  ; one  in  the  head  of  each  Twin. 

Canis  Minor,  the  Little  Dog. — This  constellation  contains 
two  large  stars.  («)  or  Procyon,  of  the  first,  and  (|3)  Mirza,  of  the  third 
magnitude,  besides  several  small  stars.  This  constellation  was  said 
to  be  one  of  the  hounds  of  Orion. 

Canis  Major,  the  Great  Dog.— ^This  constella.’on  is  to  the 
southeast  of  Orion,  and  contains  the  star  Sirius,  the  brightest  star  in 
the  whole  heavens.  This  is  said  by  the  Greeks  to  be  one  of  Orion’s 
hounds — but  the  Egyptians,  no  doubt,  gave  it  the  name  of  dog,  from 
the  fact  that  it  gave  them  warning  of  the  approach  of  the  inundation  of 
the  waters  of  the  Nile.  When  this  star  was  seen  in  the  direction  of 
the  source  of  the  Nile  they  moved  back  from  the  river  upon  the  high 
ground — and  as  the  dog  was  ever  watchful  to  announce  the  approach 
of  danger,  they  gave  the  same  name  to  this  star,  which  they  fancied 
warned  them,  although  silently,  of  approaching  danger. 

Leo  Major,  the  Great  Lion. — The  principal  star  in  this  con- 
stellation is  ('n)  or  Regulus  : it  is  on  the  meridian  at  the  time  for 
observation,  ana  about  30  degrees  south  of  the  zenith.  There  are 
several  bright  s'ars  in  this  constellation.  The  stars  in  the  head  and 
neck  form  a curve  somewhat  like  a sickie,  Regulus  being  in  the  end  of 
the  handle.  Tnis  Lion  was  supposed  to  be  a metamorphosis  of  the 
Nemasan  Lion,  which  was  slain  by  Hercules. 

Bootes,  tba  Herdsman. — This  is  a very  large  constellation, 
southeast  of  the  Great  Bear.  The  principal  stars  are  («)  Arcturus,  of 
the  first  magnitude,  and  (e)  Izar  of  the  second  magnitude.  This  star  is 
situated  in  the  Belt  of  Bootes.  This  constellation  is  of  great  anticpiity  ; 
so  much  so  that  it  is  doubtful  from  whence  it  derived  its  name.  Bootes 


is  represented  as  walking,  holding  in  his  right  hand  a spear,  and  in  his 
left  the  leading  cords  of  the  two  dogs  Asterion  and  Chara,  which  seem 
to  be  barking  at  the  Great  Bear. 

Virgo,  the  Virgin. — This  constellation  is  east  of  Leo.  The 
principal  star  is  («)  Spica,  of  the  first  magnitude,  in  the  ear  of  corn, 
which  the  Virgin  holds  in  her  left  hand,  and  is  the  only  bright  star  in 
this  constellation.  The  position  of  this  star  has  been  determined  with 
great  exactness  for  the  benefit  of  navigators.  It  is  situated  within  the 
zone,  in  the  heavens  traversed  by  the  moon.  The  moon’s  distance 
from  the  star  is  used  for  determining  the  longitude  at  sea.  According 
to  the  ancient  poets,  this  constellation  represented  the  virgin  Astroea,  the 
goddess  of  Justice,  xvho  lived  upon  the  earth  during  the  golden  age  ; but 
being  offended  at  the  wickedness  of  mankind,  during  the  brazen  and 
iron  ages  of  the  world,  she  returned  to  heaven,  aii^  was  placed  among 
the  constellations  of  the  zodiac,  with  a pair  of  scales  (Libra,)  in  one 
hand  and  a sword  in  the  other. 

Corvus,  the  Crow. — This  is  a small  constellation  south  of  the 
virgin.  It  contains  four  bright  stars,  forming  a trapezium  or  irregidar 
square.  The  brightest  of  the  two  up[)er  stars,  on  the  left,  is  called 
Algorab,  in  the  east  wing  of  the  crow.  The  crow,  it  was  said,  was 
once  of  the  purest  white,  but  was  changed  to  black,  its  present  color,  as 
a punishment  for  tale  bearing. 

Corona  Borealis,  the  Northern  Crown. — This  is  a small 
constellation  between  the  head  of  Bootes  and  Hercules.  It  may  be 
distinguished  by  six  principal  stars,  which  form  a circular  figure,  resem- 
bling a wreath  or  crown.  This  beautiful  cluster  of  stars  was  said  to 
be  in  commemoration  of  a crown  presented  by  Bacchus  to  Ariadne, 
the  daughter  of  Minos,  second  king  of  Crete. 

Draco,  the  Dragon. — This  constellation  coils  its  fore  part  around 
the  pole  of  the  Ecliptic,  and  its  tail  around  the  Pole  Star.  In  conse- 
quence of  its  various  windings,  perhaps  it  may  be  found  difficult  to  be 
traced.  According  to  fable.  Draco,  the  otlspring  of  Typhon,  with  a 
hundred  heads  and  as  many  v'oices.  was  the  guardian  of  the  golden 
appies  that  grew  in  the  garden  of  Hesperidos.  He  Mas  slain  by  Her- 
cuLEs,  xvho  obtained  the  apples,  and  presented  them  to  Eury'stheus. 

Canes  Venatici,  the  Grey  Hounds. — This  constellation  con- 
tains only  small  stars.  These  two  hounds,  which  Bootes  leads  xvith  a 
small  cord,  are  ^med  Asterion  and  Chara. 

Coma  Berenices — Berenices  Hair. — This  is  a small  constel- 
lation between  the  Greyhounds,  on  the  north,  and  the  Virgin,  on  the 
south.  It  contains  only  small  stars. 

Crater,  the  Cup. — This  cup  is  south  of  the  Great  Lion,  and 
east  of  the  Crow.  It  contains  seven  stars,  so  situated  as  in  some 
degree  to  resemble  the  outline  of  a cup.  According  to  fable,  Jupiter 
sent  the  Crow  xvith  a cup  to  fetch  water;  but  the  bird  being  of  a 
vagrant  disposition,  wasted  his  time,  and  returning  without  the  water, 
told  Apollo  that  the  stream  was  guarded  by  a venomous  serpent.  To 
punish  the  Crow  for  this  falsehood,  Apollo  placed  him  opposite  the  cup, 
and  commanded  the  serpent  never  to  allow  him  to  drink. 

Hydra,  the  Water  Serpent. — This  is  a very  long  constella- 
tion, extending  over  100  degrees  from  west  to  east.  It  may  be  known 
by  four  small  stars  south  of  the  Crab,  and  nearly  west  of  Regulus. 
This  was  supposed  to  be  the  Lernaean  Hydra,  which  Hercules  slew. 

Sextans,  the  Sextant. — This  constellation  was  formed  by 
Hevelius  of  stars  not  included  in  the  other  adjacent  constellations.  It 
contains  only  small  stars. 

Argo  Navis,  the  Ship  Argo. — This  constellation  is  in  the  south- 
ern horizon.  'I'he  head  of  the  ship  may  be  known  by  a small  cluster  I 
of  stars  about  15  degrees  of  the  dog  st..r  Sirius.  The  greater  part 
of  this  constellation  is  below  the  horizon.  Some  said  this  was  the  cele- 
brated ship  in  which  Jason  and  his  companions  went  to  Colchis,  in 
quest  of  the  golden  fleece,  which  had  fled  from  Greece.  Others  main- 
tained that  the  ship  Argo  was  no  other  than  the  Ark  of  Noah.  | 


G2 

ILEUS  'r  R A T E D 

A S r R ()  N ()  M Y . 

1 

MAP,  FROM  JANUARY  21  TO  APRIL  17. 

[ The  Stars  and  Constellations  npon  this  Maj)  will  occupy  llic  exact  ])ositi()ns  in  llic  licavcns  as  tlicy  aro 

laid  down 

on  the  I\Iap,  at  the  times  for  observations,  as  sj)eciiied  in  the  table.  The  centre  of  the  ISIap 

rcfircscnts  the  zenith  of  New- 

York,  or  anv  ydace  situated  upon  the  ])arallcl  of  latitude  of  41°  north,  lly  occasional  observations  with  these  Maps,  the 

pupil  will  become 

familiar  with  all  the  Stars  of  the  first  magnitude  as  well  as  the  prineijial  Constellations.  The  great  advan- 

tai^e  these  Maps  have  over  all  others,  is,  that  they  show  the  whole  visible  heavens  at  the  time  given  for  observations,  and  the 

exact  positions  of  the  Stars  from  the  observer  as  well  as  from 

each  other.  For  example:— 

-On  ibc  21  St  of  J.'in 

u:iry,  at  1 

o’clock  40  minutes 

in  the  morning,  the  Stars  occupy  the  same 

positions  in  the  licavens  as  laid  down  on  the  M:ip. 

'J’ho  .Star 

Regulus,  of  the  first  magnitude,  will  be  exac  tly  on  the  merid 

an,  and  about  26°  degrees  south  of  the  zeiiilli  ; I’hocyon,  or 

the  Little  Dog, 

about  35°  degrees  west  of  Regulus;  and  Sirius,  or  the  Cheat  Dog,  southwest  of  I’rocyon,  and  near  the 

horizon.  In  this  manner  the  pupil  will  be  able  to  trace  out  the  principal  Stars  and  Constellations  with  facility. 

There  are 

many  Sectional  Maps  publisheil,  but  they  are  all  subject  to  this  one  great  objection — which  is 

, the  great  difliculty  ibe  juipil 

has  in  locating  it. 

This  objection  is  entirely  obviated  in  these  Maps.] 

1 

» 

STARS  OP  THE  FIRST  MAGNITUDE. 

NAMES  OF  THE  CONSTELLATIONS  AND  PRINCIPAL  STARS. 

AURIGA,  The  Charioteer — 

(Capella.) — This  star  is  nearly 

LEO,  The  Lion- 

— (Regulus,  THE  PRINCIPAL  STAR.) — This  Star  is 

northwest,  and  about  halfway  from  the  zenith  to  the  horizon. 

26“  south  of  the  ze.ni 

th,  and  on  the 

meridian  at  the  times  specified  in 

TAURUS,  The  Bull — (Aldebaran.) — This  star  is 

in  the  eye 

the  Table  for  j\Iap  N 

0.  1. 

of  tlie  Bull,  and  nearly  west,  and  about  20°  above  tlie  horizon. 

VIRGO,  The  Virgin — (Spica.) — This  star  is  southeast,  and  about 

ORION,  Orion — (Betelgeuse.) — Tliis  star  is  in  the 

rigiit  shoui- 

20“  above  the  horizon.^ 

der  of  Orion,  a little  south  of  west,  and  about  30“  above  the  horizon 

BOOTES,  The  Herdsman — (Arcturus.) — This  star  is  situated 

ORION,  Orion — (Rigel.) — This  star  is  in  the  left  foot  of  Orion, 

nearly  east,  and  about  40“  from  the  horizon. 

southwest  of  Beteigouse,  and  very  near  the  horizon. 

LYRA.  The  Harp — (Vega.)- 

-This  star  is  nearly  northeast,  and 

CANTS  MINOR,  Little  Dog- 

— ( Procyon. ) — Th  is 

star  is  situa* 

near  the  horizon. 

ted  southwest,  about  45°  degrees  from  tlie  horizon. 

eVGNUS,  The  Swan — (Deneb.) — This  star  is  about  22“  east 

CANIS  MAJOR,  Great  Dog- 

-(Sirius.) — This  star 

is  southwest 

of  north,  and  very  near  the  horizon,  and  perhaps  not  visible  unless 

of  Procyon,  aliont  20°  from  the  horizon.  'Phis  is  the  brightest  star  in 

the  atmosnhere  is  very  clear,  and 

the  observer  situated  upon  an  emi- 

the  heavens,  and  was  considered 

the  nearest ; but  late 

observations 

nence. 

have  demonstrated  to  the  contrary. 

1 

TABLE  OF  THE  TIMES  FOR  OBSERVATIONS. 

SHOWING 

THE  DAY  AND  HOUR  OF  THE  NIGHT  WHEN  THE 

STARS  OCCUPY  THE  POSITIONS  INDICATED  ON  THE  MAP. 

II.  M. 

II.  M.  ] 

II.  M. 

H.  M. 

JANUARY  21 

1 40 

FEBRUARY  12  12  12 

MARCH 6 10  44 

MARCH...  28 

9 16 

22 

1 36 

13  12  8 

7 10  40 

29 

9 12 

23 

1 32 

14  12  4 

8 10  36 

30 

9 8 

24 

1 23 

15  12  — 

9 10  .32 

31 

9 4 

25 

1 24 

16  11  56 

10  10  28 

APRIL 1 

9 — 

26 

1 20 

17  11  52 

....  11  10  24 

2 

8 56 

27 

1 16 

18  11  48 

12  10  20 

3 

8 52  1 

28 

1 12 

19  11  44 

13  10  16 

4 

8 48 

20 

1 8 

20  11  40 

14  10  12 

5 

8 44 

30 

1 4 

21  11  30 

15  10  8 

6 

8 40 

31 

1 — 

22  11  32 

16  10  4 

7 

8 36 

niBRUARY  1 

12  .50 

23  11  28 

17  10  — 

8 

8 32 

2 

12  .52 

24  11  24 

18  9 .56 

9 

8 28 

‘ 3 

12  48 

25  11  20 

19  9 .52 

10 

8 24 

d 

12  41 

26  11  16 

20  9 48 

11 

a 20 

! .5 

12  40 

27  11  12 

21  9 44 

12 

8 16 

1 

' 0 

12  36 

23  1 1 H 

22  9 40 

' 13 

8 12 

i 7 

12  32 

MAlfCM 1 11  4 

23  9 36 

14 

8 6 

M 

12  28 

2 11  — 

24  9 32 

15 

8 4 

0 

12  21 

3 10  .50 

25  9 23 

16 

8 — 

10 

1 2 20 

4 10  .52 

26  9 24 

17 

7 56 

1 ....  n 

12  16 

5 10  48 

27  9 20 

•TT 


01 


1 L L U S T R A T E D A S 'F  R O N O M Y . 


AN  EXPLANATIO 

It  has  been  foiiiul  l)y  olis('rvalioiis,  that  the  eartli  rt'Volves  on  its 
axis  3()5;J-  times  nearly,  while  it  is  making  one  complete  revolution 
around  the  sun,  or  while  the  sun  moves  from  either  ef|ninox  to  the  same 
equinox  again  ; consequently  the,  solar  year,  upon  which  the  seasons 
depend,  contains  nearly  363]  days.  It  will  he  seen  Irotti  this  that  tlie 
difference  lietween  a year  of  3135  days  and  the  year  as  measured  by  the 
sun,  amounts  to  one  day  in  every  four  years;  so  that  in  120  years  of 
365  days,  the  seasons  would  fall  hack  c)ne  whole  month,  or  30  davs, 
and  the  season  for  May  would  he  in  June,  and  the  season  for  June 
would  he  in  July,  &c.  In  720  years  the  longest  days  would  he  in  the 
month  of  December;  hut  in  aliout  1450  years  the  season  would  fall 
back  through  the  twelve  months,  and  would  again  corres[)ond  to  their 
present  arrangement.  In  order  to  keep  the  seasons  to  the  same 
months,  and  to  make  the  solar  and  civil  year  correspond,  one  day  more 
is  included  in  the  month  of  February,  every  fourth  year.  'J'his  woidd 
always  keep  the  solar  and  civil  year  together,  if  ihe  earth  revolved  upon 
its  axis  exactly  365]  times  while  it  was  revolving  around  the  sun,  or 
during  the  solar  year ; hut  the  earth  revolves  from  one  ecpiino.v  to  the 
same  again  in  365  days,  5 hours,  48  minnti's,  40  seconds;  which  is  11 
min.  11  sec.  less  than  365]  days  : conse()uently,  in  allowing  one  day 
in  every  four  years  is  allowing  44  min.  44  sec.  too  much  ; and  in  132 
years  it  would  amount  to  24  h.  36  min.  6 sec.,  or  more  than  one  day  : 
so  that  the  longest  day,  which  is  now  on  the  21st  of  June,  would,  in  132 
years,  be  on  the  20th  of  June,  or  one  day  earlier,  and  in  264  years  the 
longest  day  would  he  on  the  I9ih  of  .lune,  and  so  on. 

This  mode  of  reckoning  time,  by  making  every  fourth  year  a leap- 
year,  was  adopted  by  the  Council  of  Nice,  in  the  year  of  our  Lord  325, 
when  the  longest  day  in  the  year  happened  June  21st,  and  the  vernal 
equinox  March  21st.  'Phis  mode  of  reckoning  was  continued  from  the 
I year  325,  to  1752,  a period  of  1427  years  ; when  it  was  found  that  the 
i longest  day  was  on  the  lOth  ol'  June,  and  the  vernal  equinox  on  the 
10th  of  March  ; the  vernal  equinox  having  fallen  back  11  days  towards 
the  beginning  of  the  year.  To  restore  the  equinoxes  to  the  same  days 
of  the  month  in  which  they  happened  in  the  year  325,  eleven  days 


N OE  LEAP-YEAR. 

were  ordered,  by  the  Briti.sh  Covernment,  and  the  United  .Stales,  then 
British  colonies,  to  be  stricken  out  of  the  monlh  of  .September,  1752, 
by  calling  the  ,3d  day  the  I4lh  ; and  it  was  ordered  that  herealb-r  one 
leap-year  in  every  132  years,  or  3 leap-years  in  400  years,  should  h.- 
omitted:  that  i.s,  that  the  years  1700,  1800,  and  1000,  which  by  the 
Old  Styi.k  would  have  been  leap-years,  should  be  cotnmoii  years  of 
.36.5  days.  'I  his  method  gives  07  leap-years  in  every  400  years. 
I bus  400  multiplied  by  36.5,  plus  97  days  for  the  leap-vears,  givf.s 
146,097  days.  'Phis  divid(‘d  by  400  years  makes  36.5  days  -5  h.  49  min. 
12  sec.  ; making  a dilferenc(?  from  the  true,  solar  year  of  only  23 
seconds  a year ; an  error  which  amounts  only  to  one  day  in  3,866 
years. 

This  new  arrangement  is  called  the  Ni;w  Styi.k, 

I his  change  was  made  to  keep  the  equinoxes  and  solstices  to  the 
same  days  of  the  same  months,  and  to  keep  the,  time  of  celebrating 
E.\stku,  and  Ihe  other  fiuists,  fasts,  and  holydays  of  the  Episcopal 
Church,  to  the  same  seasons  of  the  year.  'I'he  Rmssians  and  some  other 
eastern  nations  continue  the  Oi.n  .Style  at  the  presen'  Sny.  'Phe  year 
1800  was  not  a leap  year  by  the  New  Style,  but  would  have  been  by 
the  Old  Style  : t .e  difference  between  the  styles  is  now  12  days. 


RULE  FOR  ASCERTAINING  WHAT  YEARS  ARE 
LEAP-YEARS. 

Divide  the  years  by  4,  and  if  there  is  no  remainder  it  is  Leap- 
Y'^ear;  if  there  is  1 remainder,  it  is  the  1st  year  after  the  leap-year; 
if  there  is  2 remainder,  it  is  the  2d  ; if  there  is  3 remainder,  it  is 
the  3d  year  after  leap-year.  The  even  centuries  are  leap-years  only 
when,  by  cutting  off  the  two  cyphers,  you  can  divide  the  other  two 
figures  without  a remainder.  Thus  19(00  is  not  divisible  by  4 without 
a remainder — consequently  it  is  not  a leap-year.  The  years  2,000, 
2,400,  2,800,  &;c.  are  leap-years;  and  2,i00,  2,200,  2,300,  2,500, 
2,600,  and  2,700  are  not  leap-years. 


EQUATION  OF  TIME. 


! It  is  observed  that  time,  as  measured  by  the  sun,  differs  from  that 
I shown  by  a clock  that  keeps  true  and  equal  time  : the  solar  day,  or 
' time  from  the  sun’s  leaving  the  meridian  of  any  place  till  he  leaves  the 
i same  again,  being  sometimes  less  than  24  hours,  and  sometimes  more  ; 

! that  is,  if  by  a true  clock,  on  any  day,  the  sun  leaves  the  meridian  of 
j any  place  at  just  12  o’clock,  it  is  either  a few  seconds  before  or  a few 
! seconds  after  12,  when  he  leaves  that  meridian  the  next  time  : it  is  a 
I few  more  seconds,  either  before  or  after  12,  when  he  leaves  that  meri- 
I dian  again  ; and  so  on,  till  in  a few  weeks  it  is  several  minutes  before 
■ or  after  12  by  the  clock  when  the  sun  leaves  the  meridian. 

It  is,  in  fact,  the  place,  and  the  meridian  of  the  place,  that  leaves  the 
^ sun  ; but  we  say  the  sun  leaves  the  meridian,  because  by  the  motion  of 
the  earth  round  its  axi.s,  the  sun  appears  to  move  round  the  earth  every 
day  ; and  by  the  motion  of  the  earth  round  the  sun,  the  sun  appears  to 
move  in  the  f>cliptic  round  the  earth  once  a year.  'Phe  motion  of  the 
earth  round  its  axis  is  always  uniform  and  equal,  never  faster  at  one 
time  than  at  anothiw  ; this  is  the  only  perfi'ctly  uniform  and  equal  mo- 
tion known  : and  the  mean  or  average  titno  of  its  revolution  from  the 
silt)  to  the  sun  again  is  24  hours;  that  is,  the  averatje  or  mean  time 
from  the  sun’s  b-aving  the  meridian  of  any  place,  till  ho  leaves  the 
same  again,  is  21  hours  ; though,  as  before,  said,  it  is  sometimes  more 
and  sometimes  less. 

'Phe  rlilferene.e  bfdween  the  time  of  the  sun’s  leaving  the  meridian, 
find  12  o’fdock,  by  a true  clock,  is  called  'Piie  Euuatio.v  of  'Piime  : tit 
greale:<t  it  is  16  min.  1.5  sec.;  this  is  on  the  last  of  October,  and  first 
of  November.  On  the  14th  of  Ajiril,  Ibth  of  June,  31st  of  August,  and 
23.1  of  Def:ember,  tliii  cfpialion  or  difTcrenc.e  is  nothing,  as  then  the 


sun  and  clock  agree ; and  these  are  the  only  days  in  the  year  on  which 
the  sun  and  clock  do  agree. 

The  Equation  depends  on  two  causes  ; — viz.  1.  The  unequal  mo- 
tion of  the  sun  in  the  ecliptic  ; — And,  2.  The  obliquity  of  the  ecliptic 
to  the  equator. 

It  has  already  been  shown  that  the  sun,  as  well  as  the  moon,  moves 
much  slower  when  in  or  near  its  apogee,  than  when  in  or  near  its  peri- 
gee ; and  that  its  true  place  is  never  the  same  as  its  mean  place,  except 
in  apogee  and  perigee.  Now  as  the  motion  of  the  earth  round  its  axis 
on  the  side  next  the  sun,  is  in  the  same  direction  as  the  apparent  motion 
of  the  sun  in  the  ecliptic,  it  is  plain  that  the  slower  the  sun  moves,  the 
sooner  will  any  place  on  the  earth’s  surface  move  round  from  the  sun 
to  the  sun  again  ; or  the  shorter  will  be  the  solar  day ; because  as  the 
earth  revolves  round  its  axis,  any  place  on  the  earth’s  surface  will  over- 
take the  sun  in  less  time  when  he  advances  through  a less  space,  than 
when  he  moves  through  a larger. 

The  first  equation  depends  upon  the  sun’s  distance  fi-om  the  perigee 
or  perihelion,  and  is  the  difierence  between  the  mean  and  true  place  >f 
the  sun,  changed  into  time.  It  is  greatest  when  the  sun  is  half  Wa,y 
between  the  aphelion  and  perihelion,  and  nothing  when  it  is  in  the 
aphelion  or  perihelion.  The  sun  is  faster  than  the  clock  while  it 
is  moving  from  the  aphelion  to  the  perihelion,  and  slower,  while  . is 
moving  from  the  perihelion  to  the  aphelion.  This  difierence,  between 
the  sun  and  clock,  when  greatest,  is  7 min.  42  sec. 

The  second  equation,  depending  upon  the  obliquity  of  the  ccliptR 
to  the  equator,  at  greatest,  is  9 min.  53  sec. — {Spofford's  Astronomy, 
page  2t).) 


I L L U S T K A 'r  ED  AS  II  0 N O M Y . 


()5 


PIUKCIPAL  CONSTELLATIONS  VISIBLE,  FROM  APRIL  18  TO  JULY  21. 


Corona  Borealis,  the  Northern  Crown. — This  constella- 
lioii  is  about  15  (Ji'grees  so^llh\^'est  of  the  zc'iiith.  Six  of  the  ]')riiicii)al 
stars  form  a circular  ligure  resembling  a wreatli  or  crown. 

Bootes,  the  Herdsman. — This  constellation  is  situated  west  of 
the  Crown.  The  principal  star  is  Akctukus. 

Hercules. — This  constellation  is  east  of  Corona  or  the  Crown, 
and  extends  from  12  to  50  degrees,  noi'th  declination.  It  contains  one 
hundred  and  nineteen  stars — one  of  the  2d  magnitude  and  one  of  the  2d 
in  the  right  shoulder.  These  are  called  Bkta  and  Ga.rma.  The  left 
or  cast  arm  of  Hercules  grasps  the  three  headed  monster  Cerbkrus. 

According  to  mythology,  this  constellation  is  intended  to  immortalize 
the  name  of  Hercules,  the  Theban,  so  celebrated  in  antiquity  for  his 
heroic  valor  and  invincible  prowess.  By  command  of  Eurysfheus,  he 
achieved  a number  of  enterprises,  the  most  difficult  and  arduous  ever 
known,  called  the  Twelve  Labors  oi<’  Hercules. 

1st.  He  subdued  the  Nemman  Lion  in  his  den,  and  clothed  himself 
in  his  skin. 

2d.  He  slew  the  I.ern.ean  Hydra,  with  a hundred  hissing  heads, 
and  dij)ped  his  arrows  in  the  gall  of  the  monster,  to  render  their  wounds 
incurable. 

3d.  lie  took  alive  the  stag  with  golden  horns  and  brazen  feet,  which 
was  famous  for  its  incredible  swiftness,  after  pursuing  it  for  twelve 
months,  and  presented  it  unhurt  to  Eurystheus. 

4th.  He  took  alive  the  Erlmanthean  Boar,  and  killed  the  Centaurs 
which  opposed  him. 

5th.  He  cleansed  the  stables  of  Augias,  where  3,000  oxen  had  been 
confined  for  many  years. 

Gth.  He  killed  the  carnivorous  birds  which  ravaged  the  country  of 
Arcadia,  and  fed  on  human  flesh. 

7th.  He  toolc  alive,  and  brought  into  Peloponnesus,  the  wild  bull  of 
Crete,  which  no  mortal  durst  look  upon. 

Sth.  He  obtained  for  Eurystheus  the  iMares  of  Diomedes,  which  lived 
on  human  flesh,  after  having  given  their  owner  to  be  first  eaten  by 
them. 

9lh.  He  obtained  the  girdle  of  the  Queen  of  the  Amazons,  a formida- 
ble nation  of  warlike  females. 

^ loth.  He  killed  the  monster  Geryon,  king  of  Gades,  and  brought 
away  his  numerous  flocks,  which  fed  upon  human  flesh. 

llth.  He  oV)tained  the  Golden  Apples  from  the  Garden  of  Hespe- 
rides,  which  were  watched  by  a dragon. 

12th.  He  finally  brought  up  to  the  earth  the  three  headed  dog  Cer- 
berus, who  guarded  the  entrance  to  the  infernal  regions. 

Lyra,  the  Harp. — This  is  a small  but  beautiful  constellation.  It 
contains  («)  Vega,  one  of  the  brightest  stars  in  the  northern  hemis- 
phere, and  is  situated  directly  east,  and  between  30  and  45  degrees 
from  the  zenith. 

It  is  asserted  that  this  is  the  celestial  Lyre  which  Apollo  or  Mer- 
! cury  gave  to  Crpheus,  and  upon  which  he  played  with  such  a masterly 
hand,  that  even  the  most  rapid  rivers  ceased  to  flow;  the  wild  beasts 
of  the  forest  forgot  their  wildness,  and  for  the  time  being  became  tame, 
and  the  mountains  came  to  listen  to  his  song. 


Aquila,  tlie  Eagle. — T'  s constellation  may  be  easily  found  by 
three  stars  in  a riglit  line;  Altxir,  of  the  first  magnitude,  midway 
between  the  other  two. 

'Phis  constellation  is  supposed  to  have  been  Merops,  a king  of  the 
Island  of  Cos.  who  was  transformed  into  an  Eagle,  and  i>laced  among 
the  constellations. 

DelpMntls,  the  Dolphin. — This  is  a beautifij!  little  cluster  of 
stars,  and  may  be  easily  distinguished  by  four  principal  stars  in  the 
form  of  a diamond.  The  Dolphin  was  made  a constellation  for  persuad- 
ing the  goddess  Amphitrite,  who  had  made  a vow  of  perpetual  celibacy, 
to  become  the  wife  of  Neptune. 

OphiuchilS,  the  Serpent  Bearer. — This  constellation  is  repre- 
sented as  a man  with  a long  be§.rd,  holding  in  his  clenched  hands  a 
prodigious  Serpent,  which  is  writhing  in  his  grasp.  This  constellation 
occupii's  a large  space,  from  15°  north  to  25°  south  of  the  equator, 
d'he  principal  star  is  Ras  Alhague,  of  the  second  magnitude,  situ- 
ated  in  the  head.  The  star  on  the  foot  just  south  of  the  ecliptic  is 
Riio.  According  to  mythology,  Obhiuciius  or  Esculapius,  as  he  was 
sometimes  called,  was  the  god  of  Medicine.  He  was  the  son  of  Apollo, 
but  was  killed  by  Jupiter  with  a thunderbolt,  for  restoring  Ilippolytus  .o 
life. 

Scorpio,  the  Scorpion. — This  is  one  of  the  constellations  of 
the  zodiac.  It  is  a very  beautiful  group,  as  it  contains  one  star  of  the 
first,  two  of  the  second,  and  eleven  of  the  third  magnitude.  («)  An- 
tares,  of  the  first  magnitude,  is  situated  in  the  heart  of  the  Scorpion.  It 
is  a little  east  of  the  meridian,  and  about  20  degrees  above  the  horizon. 
Orion,  a celebrated  giant,  having  impiously  boasted  that  there  was  no 
animal  on  earth  which  he  could  not  subdue,  Diana,  whom  he  had 
offended,  sent  a Scorpion,  which  stung  him  to  death. 

Serpens,  the  Serpent. — This  constellation  is  united  with  that 
of  Opiiiuchus,  who  holds  the  serpent  in  his  grasp.  It  may  be  distin- 
guished by  several  bright  stars  in  and  near  the  head 

Libra,  the  Scales. — This  constellation  contains  4 stars  of  the 
2d  magnitude,  by  which  it  may  be  distinguished  ; two  of  them  being 
about  10  degrees  northwest  of  Antares  in  the  Scorpion.  About  twenty- 
two  hundred  years  ago  this  constellation  coincided  with  the  sign  Libia 
of  the  ecliptic,  and  when  the  sun  entered  this  constellation  the  days  and 
nights  were  equal  ; hence  it  was  very  appropriately  represented  by  the 
ancients  by  a pair  q^cales,  which  denote  equality. 

Scutum,  or  Sobieski’s  Shield. — This  is  a small  constellation, 
instituted  by  Hevelius.  It  may  be  known  by  three  small  stars  in 
the  form  of  a triangle. 

Vulpecula  et  Anser — (The  Fox  and  Goose.) — This  constel- 
lation was  also  established  by  Hevelius,  and  is  situated  south  of  he 
Swan  and  north  of  the  Dolphin  and  Eagle.  It  contains  only  small 
stars. 


I L I.  IJ  8 '1'  K A r i:  0 A S 'r  R ()  N ()  i\I  Y . 


1 


(if) 


MAP,  FROM  APRIL  18  TO  JULY  21. 

[ !It^“  The  Stars  and  Constellations  upon  this  Map  will  occupy  the  exact  j)ositions  in  the  heavens  as  lliey  arc  laid  down 
on  the  Map,  at  the  times  for  observations,  as  S})ecilied  in  the  table.  The  centre  of  the  Map  represents  the  zenith  of  New- 
A ork,  or  an^'  ^jlace  situated  upon  the  parallel  of  latitude  of  41°  north,  d’here  will  he  eight  stars  of  the  first  magnitude  visi- 
ble, the  most  conspicuous  of  which  will  be  Arcturus,  Vega,  Altair,  Dcneb,  Atitares,  and  Sj>ica.  The  other  two  being  near  the 
horizon,  may  not  be  visible  unless  the  atmosphere  is  very  clear.] 


STARS  OF  THE  FIRST  MAGNITUDE. 


NAMES  OF  THE  CONSTELLATIONS  AND  PRINCIPAL  STARS. 

BOOTES,  The  IIekdsman — (Arcturus  the  principal  star.) — 
This  star  is  situated  towards  the  southwest,  and  about  80°  from  the 
zenith 

■9 

YIRGO,  The  Virgin — (Spica.) — This  star  is  almost  in  a direct 
line  southwest  of  Arcturus,  and  about  30°  above  the  horizon. 

LYRA,  The  Harp — (Vega.) — This  star  is  due  east  and  about  37° 
from  the  zenith. 

LEO  MAJOR,  The  Great  Lion — (Regulus.) — This  star  is  due 
west,  and  about  10°  above  the  horizon — perhaps  not  visible  unless  the 
atmosphere  is  very  clear. 


AQUILA,  The  Eagle — (Altair.) — 'I'liis  star  is  nearly  sontlictist 
of  V^ega,  and  about  half  way  from  Vega  to  the  horizon. 

CYGNUS,  IhiE  Swan — (Deneb.) — 'I’his  star  is  nearly  northeast 
of  the  zenith  and  east  of  the  North  Star. 

AURIGA,  The  Charioteer — (Capella.) — 'I’his  star  is  about 
10°  west  of  north,  and  very  near  the  horizon  ; perha[)3  not  visible. 

SCORPIO,  'J'liE  Scorpion — (Antares.) — 'Phis  star  is  nearly 
south,  being  only  about  20°  east  of  the  meridian.  It  is  about  30° 
above  the  southern  horizon.  There  are  two  stars  of  the  second  magni- 
tude about  10°  to  the  northwest  of  it. 


TABLE  OF  THE  TIMES  FOR  OBSERVATIONS, 

SHOWING  THE  DAY  AND  HOUR  OF  THE  NIGHT  WHEN  THE  STARS  OCCUPY  THE  POSITIONS  INDICATED  ON  THE  MAP. 


APRIL. 


iM 


H. 

M. 

1 

H. 

M. 

II. 

51. 

H. 

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JUNE... 

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JUNE.. 

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9 

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. . • • 

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9 

24 

20 

2 

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7 

10 

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JULY.. 

...  1 

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20 

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2 

4 

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8 

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STARS  VISIBLE 


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PRINCIPAL  CONSTELLATIONS  VISIBLE,  FROI  JULY  21  TO  OCTOBER  31. 


Cygnus,  the  Swan. — Tliis  constellation  is  situated  a little  to  the 
west  of  the  zenith.  It  is  re|n-cscnted  with  outspread  wings,  flying  in 
the  direction  of  the  milky  way  to  the  southwest.  'Fhe  five  principal 
stars  are  so  arranged  as  to  form  a large  and  regular  Cross.  Deneb,  a 
star  of  the  first  magnitude,  is  in  the  head  of  the  Cross,  and  Alhirf.o, 
situated  in  the  beak  of  the  Swan,  forms  the  foot.  Over  the  right  wing 
of  the  Swan  is  a remarkable  double  sta:r,  known  by  the  name  of  “ 61 
Cygni.”  These  stars  are  of  the  .bth  and  6th  magnitude  ; they  revolve 
round  a common  centre  of  gravity  between  the  two,  in  .540  years. 
These  two  stars  will  over  be  memorable  as  being  the  first  whose  dis- 
tance from  us  was  measured  with  much  precision,  and  are  the  nearest 
to  us,  with  a single  exception,  of  any  as  yet  known.  The  star  (a)  Cen- 
tauri  is  about  one-third  the  distance  of  61  Cygni.  Observations  have 
been  made  on  a great  many  others  ; but  their  parallax  is  much  less, 
and  in  most  cases  is  so  small  as  not  to  be  perceptible  with  the  most 
accurate  instruments.  The  distance  of  61  Cygni  was  ascertained  by 
Bessel,  from  his  observations,  in  the  years  1837,  183S  and  1839.  He 
found  their  distance  592,000  times  the  earth’s  mean  distance  from  the 
sun.  So  great  is  this  distance,  that  a canyon  ball,  moving  500  miles 
an  hour,  would  not  reach  those  two  stars  in  less  than  thirteen  millions 
of  years.  The  sun,  seen  from  these  stars,  would  appear  like  a star  of 
the  5th  magnitude.  Previous  to  this  discovery  the  stars  were  consider- 
ed to  be  about  the  same  in  magnitude,  and  the  brightest  stars  to  owe 
their  brilliancy  to  their  being  nearer  to  us ; but  the  brightest  star  in  the 
whole  heavens  (Sirius,  the  great  Dog  Star,)  is  at  a much  greater  dis- 
tance than  these,  and  owes  its  brilliancy  to  its  superior  magnitude  or 
much  greater  brilliancy. 

Lyra,  the  Harp. — This  constellation  is  next  to  the  Swan.  For 
a description  of  this  constellation,  see  explanations  to  Map  No.  2,  from 
April  18  to  July  31. 

Cepheus,  the  King. — This  constellation  may  be  known  by  three 
stars  of  the  third  magnitude  in  a right  line — in  the  neck,  breast, 
and  knee.  He  stands  xvith  his  left  foot  over  the  pole.  He  holds  a 
sceptre  in  his  hand,  extended  towards  Cassiopeia,  his  wife.  Cepheus 
was  the  king  of  Ethiopia  : the  name  of  his  queen  was  Cassiopeia.  He 
was  one  of  the  Argonauts  who  accompanied  Jason  in  his  expedition 
from  Greece  to  Colchis,  in  quest  of  the  Golden  Fleece,  and  at  his  death 
was  changed  into  a constellation. 

Cassiopeia,  the  Lady  in  her  Chair. — This  constellation  is 
situated  east  of  Cepheus.  She  is  represented  in  regal  state,  seated  on 
a throne  or  chair,  holding  in  her  left  hand  the  branch  of  a palm  tree. 
She  is  surrounded  by  her  royal  family — Cepheus,  her  husband,  on  her 
right  hand  ; Perseus,  her  son-in-law,  on  her  left,  and  Andromeda,  her 
daughter,  just  above  her.  This  constellation  contains  55  stars,  that  are 
v.sible  to  the  naked  eye  : five  of  these  are  of  the  3d  magnitude,  which, 
^vith  two  smaller  ones,  form  a figure  resembling  an  inverted  chair. 

Cassiopeia  was  the  wife  of  Cepheus,  king  of  Ethiopia.  She  xvas 
possessed  of  great  beaut}',  and  boasted  herself  fairer  than  Juno,  the  sis- 
ter of  Jupiter,  or  the  Nereides,  a name  given  to  the  sea  nymphs.  This 
provoked  the  nymphs  of  the  sea,  who  complained  to  Neptune,  of  the 
insult.  He  sent  a frightful  monster  to  punish  her  Insolence.  It  was 
finally  ordained  that  she  should  chain  her  daughter  Andromeda,  xvhom 
she  tenderly  loved,  to  a desert  rock  on  the  beach,  and  leave  her  expo- 
sed to  the  fury  of  this  monster.  She  was  thus  left,  and  the  monster 
approached ; but  as  he  was  going  to  devour  her,  Perseus  killed  him. 

Andromeda. — This  constellation  is  south  of  Cassiopeia.  It  con- 
tains 66  stars,  three  of  xvhich  are  of  the  third  magnitude,  viz:  Sirrah, 
in  the  head  ; Mirach,  in  the  breast,  and  Alrnak,  in  the  feet.  They 
stand  nearly  in  a straight  line.  Andromeda,  the  daughter  of  Cepheus 
and  Cassiopeia,  was  exposed  to  be  devoured  by  a Sea  Monster,  to 
appease  the  wrath  of  Neptune.  She  xvas  accordingly  chained  to  a rock 
neai  Joppa,  (now  Jaffa  in  Syria,)  and  at  the  moment  the  monster  was 
going  tq  devour  her,  Perseus,  who  xvas  returning  through  the  air  from 
the  conquest  of  the  Gorgons.  saw  her  and  was  captivated  by  her 
beauty.  He  promised  to  deliver  her  and  destroy  the  monster,  if  her 
father  would  give  her  to  him  in  marriage.  Cepheus  consented,  and 


Perseus  instantly  changed  the  sea  monster  into  a rock,  by  showing  liim 
Medusa’s  head,  which  was  still  reeking  in  his  hand.  This  fable  of 
Andromeda  and  the  sea  monster  might  mean  that  she  was  courted  by 
some  monster  of  a sea  captain,  who  atte^npted  to  carry  her  away,  but 
xvas  prevented  by  another  more  gallant  and  successful  rival. 

Pegasus,  the  Flying  Horse. — This  constellation  is  represented 
with  wings.  It  may  be  known  by  four  stars,  xvhich  form  a regular 
quadrangle  or  trapezium.  The  northeastern  of  these  four  stars  is  in  the 
head  of  Andromeda.  Their  names  are  («)  Markab,  ((?)  Scheat,  Alge- 
nib,  and  («)  Sirrah,  in  the  head  of  Andromeda.  According  to  fable, 
Pegasus  was  a winged  horse,  which  sprang  from  the  biood  of  RIedusa, 
when  Perseus  cut  off  her  head. 

Equuleus,  the  Little  Horse. — This  is  a small  cluster  of  stars 
west  of  the  head  of  the  Flying  Horse.  Only  the  head  is  visible.  This 
is  supposed  to  represent  the  horse  which  Mercmy  gave  to  Castor,  and 
which  he  named  Celeris. 

Lelphinus,  the  Dolphin. — This  is  a beautifijl  little  constella- 
tion, between  the  Eagle  and  Equuleus,  or  Little  Horse.  It  may  be  dis- 
tinguished by  four  stars  in  the  shape  of  a diamond,  with  two  small  stars 
w'hich  form  the  tail.  (See  map  No.  2,  and  explanation.) 

Sagittarius,  the  Archer. — This  is  the  tenth  constellation  in 
the  zodiac.  It  is  situated  to  the  southwest,  near  the  horizon.  It  may 
be  known  by  five  stars,  forming  a figure  resembling  a short  handled 
dipper.  It  appears  turned  up,  with  the  handle  to  the  north,  and  the 
bowl  towards  the  east.  Sagittarius,  or  Chiron,  the  son  of  Saturn, 
was  a twofold  being — half  man  and  half  horse.  Ti'his  constellation  xvas 
intended,  ho  doubt,  by  the  ancients  to  represent  the  season  for  hunt- 
ing  ; for  xvhen  the  sun  enters  this  sign,  the  trees  have  cast  their  foliage, 
xviiich  enables  the  hunter  to  pursue  his  game  to  better  advantage. 

Capricomus,  the  Goat. — This  is  the  next  sign  in  the  ecliptic, 
east  of  Sagittarius.  There  are  two  conspicuous  stars  in  ihe  head, 
called  Gie.di  and  Dabih.  Giedi  is  the  most  northern  star  of  the  txvo, 
and  is  double.  Several  other  stars  may  be  traced  out  by  refe?-ence  to 
the  map.  The  goat  xvas  observed  by  the  ancients  to  be  fond  of  climb 
ing  high  mountains  and  lofty  precijiices,  and  xvas  therefore  considered 
emblematical  of  the  sun,  xvhich,  having  in  this  sign  reached  his  great  • 
est  southern  declination,  begins  to  re-ascend  towards  the  north. 

Aquarius,  the  Water  Bearer. — This  constellation  is  repre- 
sented by  the  figure  of  a man  pouring  out  xvater  from  an  urn,  and  is 
north  and  east  of  Capricomus.  It  may  easily  be  traced  by  reference  to 
the  map.  The  ancient  Egyptians  supposed  the  disappearing  of  Aqua- 
rius caused  the  xx'aters  of  the  Nile  to  rise  by  the  sinking  of  bis  urn  in 
the  xvater. 

Pisces,  the  Fishes. — This  is  the  last  sign  in  the  ziy-riac,  This 
constellation  is  represented  by  txx'o  fishes,  a considerable  distance  apart, 
tied  by  a cord  or  ri’oand.  The  stars  in  this  constellalinn  are  of  the 
4th  and  inferior  magnitudes.  The  probable  origin  of  this  sign  xvas 
from  the  fact,  that  xvhen  the  sun  xx'as  in  it,  it  xvas  the  season  xvhen  fish 
xvere  abundant,  and  easily  taken. 

Piscis,  the  Southern  Fish. — This  constellation  is  south  of 
Aquarius,  and  is  easily  distinguished  by  the  star  Fomalhaut,  of  the  first 
magnitude,  xvith  two  small  stars,  xvhich  form  an  equilateral  triangle. 
These  three  are  the  only  imjiortant  stars  in  this  constellation.  This 
constellation  is  supposed  to  have  taken  its  name  from  the  transformation 
of  Venus  into  the  shape  of  a fish,  xvhen  she  fled,  terrified  at  the  horrible 
advances  of  the  monster  Typhon,  xvho  was  said  to  have  an  hundred 
heads.  [ 

ITrsa  IMajor,  the  Great  Bear. — This  constellation  is  directly  I 
north,  atid  touches  the  horizon.  The  Dipper,  xvhich  is  a part  of  this 
constellation,  is  a little  to  the  northwest  of  fhe  north  star,  and  is  right 
side  up,  xvith  the  handle  to  the  west.  (For  explanation,  see  map  No.  1.) 

Lacerta,  the  Lizard. — This  is  a small  constellation  near  the. 
zenith.  It  contains  a fexv  stars  of  inferior  magnitude. 


f 


1 L L U S T R A T I*:  DAS  '1'  R ()  N O M Y . 


I , MAP,  FPiOM  JULY  22  TO  OCTOItl'R  31. 

I [ The  Stars  nnd  Conslcllalions  upon  this  IVIap  will  oocnpy  the  exact  positions  in  the  hea  vens  ns  ihcy  arc  laid  down 
on  the  Map,  at  the  times  for  observations,  as  specified  in  the  talile.  'J'he  centre  of  the  Map  rcprc.senls  the  zenith  of  New- 
\ ork,  or  any  place  situated  upon  the  parallel  of  latitude  of  41®  north.  There  will  he  only  six  stars  of  the  first  magnitude 
visilile,  the  most  conspicuous  of  which  will  be  Deneh,  Vega,  Altair,  and  Capella.  'I’lie  other  two,  Aldcharan  and  Fomalhaut, 
being  near  the  horizon,  may  not  be  visible  unless  the  atmosphere  is  very  clear.] 


STARS  OF  THE  FIRST  MAGNITUDE. 


NAMES  or  THE  CONSTELLATIONS  AND  PRINCIPAL  STARS. 

CYGNUS,  The  Swan — (Deneb  the  principal  star.) — This 
star  is  situated  directly  west,  and  about  20'^  from  the  zenith.  It  is  in 
the  middle  of  the  Milky-way. 

LYR.\.,  The  Harp — (Vega.) — Tiiis  star  is  about  20°  west  of 
1 1 Deneb. 

i i - 

j AQITLA,  The  Eagle — (Altair.) — This  star  is  situated  towards 

i the  southwest,  and  about  from  the  zenilh- 

I 


PISCIS,  Southern  Fish — (Fomalhaut.) — This  star  is  about 
10°  cast  of  south,  and  about  l.j°  above  the  sonllici  n horizon — perh.'i|).s 
it  will  not  be  visible  only  when  the  atmosphere  is  clear. 

TAURUS,  The  Ruli. — (Aldebaran.) — 'Phis  star  is  nearly  north- 
east, and  within  10“  of  the  horizon.  It  will  not  be  visible  only  when 
the  atmosphere  is  very  clear. 

aURIGA,  The  Charioteer — (Capella.) — Tliis  star  is  directly 
east  of  the  North  Star,  and  about  midway  to  the  horizon. 


TABLE  OF  THE  TIMES  FOR  OBSERVATIONS. 


SHOWING  THE  DAY  AND  HOUR  OF  THE  NIGHT  WHEN  THE  STARS  OCCUPY  THE  POSITIONS  INDICATED  ON  THE  MAP. 


H. 

M. 

It. 

M. 

1 

ir. 

M. 

♦ 

H. 

M. 

JULY 

22 

1 

56 

AUGUST... 

17 

12 

12 

SEPTEMBER  12 

10 

28 

OCTOBER. 

•. . 8 

8 

44 

1 

23 

1 

52 

18 

12 

8 

• • • • 

13 

10 

24 

• • • • 

9 

8 

40 

! 1 

24 

1 

48 

19 

12 

4 

• • « • 

14 

10 

20 

• • • • 

10 

8 

36 

, i 

; 1 • • • • 

25 

1 

44 

20 

12 

— 

• • • • 

15 

10 

16 

• • • • 

11 

8 

32 

; 1 

1 1 • • • • 

20 

1 

40 

21 

11 

56 

• • • • 

16 

10 

12 

• • • • 

12 

8 

28 

1 

1 • • « • 

27 

1 

36 

22 

11 

52 



17 

10 

8 

• • • • 

13 

8 

24 

1 

29 

1 

32 

23 

11 

48 

• • • • 

18 

10 

4 

• • • • 

14 

8 

20 

29 

1 

28 

24 

11 

44 

\ . . . . 

19 

10 

— 

15 

8 

10 

80 

1 

24 

25 

11 

40 

20 

9 

50 

10 

8 

12 

31 

1 

20 

26 

11 

36 

« « • • 

21 

9 

52 

• • • . 

17 

8 

8 

AUGU.ST.. 

1 

1 

16 

27 

11 

32 

• • • • 

22 

9 

48 

18 

8 

4 

2 

1 

12 

28 

11 

28 

• • • • 

23 

9 

44 

19 

8 

— 

r • • • • 

3 

1 

8 

29 

11 

24 

« • « • 

24 

9 

40 

20 

7 

50 

i 

4 

1 

4 

30 

11 

20 

• • • • 

25 

9 

36 

• • • • 

21 

7 

52 

1 .... 

5 

1 

— 

31 

11 

16 

1 • • • • 

26 

9 

32 

• • • • 

22 

7 

48 

i • • • • 

0 

12 

56 

SEPTEMHER 

1 

11 

12 

• • • • 

27 

9 

28 

• • • • 

23 

7 

44 

7 

12 

52 

2 

11 

8 

• « • • 

28 

9 

24 

• • • • 

24 

7 

40 

9 

12 

48 

3 

11 

4 

• * • • 

29 

9 

20 

25 

7 

36 

1 

1 

9 

12 

44 

4 

11 

— 

• • • • 

30 

9 

16 

26 

7 

32 

1 

10 

12 

40 

5 

10 

50 

OCTOBER. 

..  1 

9 

12 

.... 

27 

7 

28 

11 

12 

36 

fl 

10 

52 

• • • • 

2 

9 

8 

.... 

28 

7 

24 

1 

12 

12 

32 

7 

10 

48 

» • • • 

3 

9 

4 

.... 

29 

7 

20 

1 

13 

12 

28 

8 

10 

44 

• * * • 

4 

9 

— 

• • • • 

30 

7 

10 

■ i 

1 • • • • 

11 

12 

21 

9 

10 

40 

• • • • 

5 

8 

56 

.... 

31 

7 

12 

1.5 

12 

20 

10 

10 

36 

• • • • 

0 

8 

52 

10 

12 

10 

11 

10 

32 

.... 

7 

8 

48 

I 


Fast 


1 1,  1,  US'l’  11  A '1'  !•:  1)  A8'r  llON  O.M  Y. 


ZODIACAL  LIOIIT. 


The  Zodiacal  Ligilt  is  a faint  luminous  appearance,  wliich  accom- 
panies the  Sun,  and  is  seen  just  after  twilight  in  the  evening,  or  before 
it  commences  in  the  morning.  It  was  observed  by  Kepler,  who  sup- 
posed it  to  be  the  Sun’s  atmosphere,  and  afterwards  accurately  described 
by  Cassim,  in  1683,  who  gave  it  the  name  by  which  it  is  now  known, 
in  consequence  of  its  always  being  in  the  Zodiac.  It  probably  sur- 
rounds the  sun  on  all  sides  ; but  is  shaped  like  a lens,  or  burning  glass, 
the  circumference  of  which  is  directly  over  the  Sun’s  equator.  The  edge 
being  always  presented  to  us  gives  it  the  appearance  of  a pyramid  or 
cone.  There  can  only  that  portion  of  it  be  seen  which  remains  above 
the  horizon  after  twilight  has  ceased.  When  seen,  it  extends  from  the 
horizon  upwards,  and  following  the  course  or  path  of  the  Sun.  For 
this  reason  it  is  scarcely  visible  in  our  latitude,  as  the  path  of  the  .Sun 
during  most  of  the  year,  is  very  oblique  to  the  horizon  : consequently 
it  is  obscured  by  twilight,  which  does  not  cease  until  the  Sun  is  18 
degrees  below  the  horizon.  At  the  equator  it  can  be  favorably  observed 
most  of  the  year,  and  often  presents  a beautiful  appearance.  The 
most  favoiable  times  for  observing  it  in  our  latitude  are  in  the  evening, 
during  the  months  of  April  and  May,  and  in  the  morn’ing  during  the 
months  of  Octoljer  and  November,  as  the  path  of  the  sun  is  nearer  per- 
pendicular to  the  horizon  than  at  any  other  times  during  the  year.  It 


appears  in  form  like  a pyramid,  with  the  base  nt  the  horizon — tapering 
to  a point,  and  more  or  less  inclined  to  tin*  horizon. 

Il.s  length  above  the  horizon  varies,  accorditig  to  cirriimstnnci's,  from  i 
40  to  loo  di'grees,  and  its  breadth  at  the  base  perpendieulnr  tf)  its  axis 
vai'ies  from  8 to  3(J  (h'grees.  It  is  extremely  faint  and  ill-defined  in 
our  climate  ; but  is  much  more  conspicuous  in  tro|)ical  coiinlries.  An 
allusion  is  maih;  to  this  phenomenon  >n  a work  piddished  by  .1.  (Mdl- 
drey  in  lOfil,  in  the  fiillowing  passage  : — “In  the  month  of  February, 
fin-  several  ytuirs,  about  six  o’clock  in  the  evening,  after  twilielil,  1 saw 
a path  of  light  tending  from  the  twilight  tr)warrls  the  I'leitidi's,  as  it  were 
touching  them  : this  is  to  be  seen  whenever  the  weather  is  clear,  but 
best  when  the  moon  does  not  shine.  I believe  that  this  phenomenon 
h;i3  been  befon;  visible,  and  will  hereafter  tippear,  always  at  the  above 
mentioned  period  of  the  year;  but  the  cause  and  nature  of  it  1 cannot 
guess,  and  therefore  leave  it  to  the  inquiry  of  posterity.” 

Various  opinions  and  theories  have  been  advanced  by  a.stronomers, 
both  ancient  and  tnodern  ; but  none  have  been  able  to  settle  the  point 
beyond  controversy.  Cassini  thought  it  might  proceed  fiom  an  innu- 
merable multitude  of  little  bodies  rttxadving  around  the  ,Stin,  reflectinjr  a 
faint  light,  like  that  of  the  rnilky-way.  Kepler  ascribed  ita  appeaiaiice 
to  the  atmosphere  which  he  supposed  to  surround  the  Sun.  Iloth  of 
these  theories  have  been  discarded  as  being  untenable.  Professor 
Olrnstead  supposes  it  to  be  a nebulous  body,  or  thin  gaseous  rnas.s, 
revolving  around  the  Sun,  causing  the  Meteoric  Showers  that  have 
occurred  for  several  years  in  the  month  of  November,  in  conseciuence 
of  the  earth’s  near  approach  to  it,  in  its  annual  course  around  the  Sun. 

Ilerschell  and  Professor  Nichol  assert  that  the  Zodiacal  flight  is  a 
phenomenon  precisely  similar  to  that  exhibited  by  the  nebulous  stars,  j 
and  if  we  were  living  upon  some  distant  star,  the  Sun  would  appeal 
to  us  like  a star  surrounded  by  a faint  light  similar  to  that  of  a candle 
seen  at  a short  distance,  in  a foggy  or  thick  atmosphere. 

The  present  theory  of  the  Zodiacal  Light  may  be  summed  up  in  a 
few  word.s — namely,  that  the  matter  of  which  the  Sun  and  planets  are 
composed  was  originally  in  a thin  gaseous  state,  and  has  been  con- 
densed into  solid  bodies,  which  form  the  Sun  and  planets ; that  the 
Zodiacal  Light  is  a portion  of  this  matter,  which  has  not  as  yet  subsided 
into  the  Sun.  It  is  estimated  to  extend  beyond  the  orbit  of  Mercury, 
and  perhaps  that  of  Venus  ; if  so,  they  must  pass  through  it  twice  during 
each  revolution  around  the  Sun. 


A mWLE  METHOD  TO  FJND  THE 

All  circles,  great  or  small,  are  sn[)posed  to  be  divided  into  360  equal 
parts,  called  degrees.  I’rom  this  it  will  be  seen  that  a degree  has  no 
deliniie  measure;  but  depends  u[)on  the  magnitude  of  the  circle.  If  we 
su(»pose  a circle  to  be  360  iiules  in  circumliu'ence,  then  one  degree, 
would  mrs'isure  just  one  mile  ; but  if  th(?  circle,  were  greatc'r  a degree 
would  be  greater,  and  if  less  a degnu;  would  be  h’ss.  VVe  will  now 
apply  this  principle  of  the  circle  to  measure  the  circumferences  of  the 
eaiih.  In  order  to  do  this,  wi'  must  take  two  places  some  di.stance 
apart  and  under  the  same  meridian  ; we  vviil  suppose  New  York 
and  Albany. 

e will  suppose  that  the  exact  rlislance  belw(‘en  the  two  [ilacf'S  has 
been  |r,iiti'l  by  exact  meuhiiremeiit  to  be  138J  miles — (this  distance 


CIRCUMFERENCE  OF  THE  EARTH. 

probably  does  not  vary  much  from  the  truth.)  We  xvill  now  place  an 
observer  at  each  place  with  accurate  instruments,  and  on  a particular 
night,  at  1*3  o’clock,  the  observer  at  New  York  finds  a particular  star 
exactly  in  his  zenith,  or  over' head;  but  the  observer  at  Albany  finds 
the  same  star  two  degrees  to  the  south  of  his  zenith, — hence  it  will  be 
seen  that  there  are  two  degrees  between  the  two  places  ; and  as  the 
distance,  by  measurement,  was  found  to  be  138J  miles,  the  two  degrees 
Ix'tween  New  York  and  Albany  arc  eipial  to  138.^  miles,  or  one 
degree  eipials  6!).^  inih^s.  Now,  if  we  multiply  the  number  of  de- 
gr(^os  in  (he  whole  circle  or  circumference  of  the  earth  (360)  by 
6!),j  miles,  it  will  give  24,930  miles  the  whole  circumference  of 
the  earth. 


I L L U S T R A T E D A S T R O N O M Y . 73 


PRINCIPAL  CONSTELLATIONS  VISIBLE,  FROM  NOVEMBER  1 TO  JANUARY  20. 


Perseus,  and  Medusa’s  Head. — This  constellation  is  directly 
in  the  zenith,  or  over  head.  It  contains  two  stars  of  the  ^d  magnitude. 
The  one  in  the  breast  of  PnusKus  is 'called  Mirzak,  or  Algenib;  the 
other  is  Algol,  in  Medusa’s  head  : it  is  about  I.*}®  east  of  the  zenith. 
This  star  is  remarkable  on  account  of  its  changeableness.  It  changes 
in  4 hours  from  the  2d  to  the  4th  magnitude.  It  remains  in  this  condi- 
tion 18  minutes,  when  it  begins  to  increase  in  brightness  ; and  in  4 
hours  and  40  minutes  appears  again  of  the  2d  magnitude  : in  which 
state  it  continues  G1  hours,  when  it  begins  to  diminish  again.  Dr.  Her- 
schel  attributes  its  variableness  to  spots  upon  its  surface  like  those  of 
the  sun,  and  that  it  revolves  upon  its  axis. 

[^Hislory. — Perseus  was  the  son  of  Jupiter  and  Dan.e.  He  w'as  no 
sooner  born  than  he  was  cast  into  the  sea  with  his  mother,  and  was 
driven  on  the  coast  of  one  of  the  islands  of  Cyclades.  Polydectes, 
the  King  of  the  place,  treated  them  with  kindness,  and  placed  them 
in  the  care  of  the  Priests  of  Minerva’s  Temple.  He  promised  to  pre- 
sent the  King  with  the  head  of  Medusa,  the  only  one  of  the  Gorgons 
who  was  subject  to  mortality.  They  were  represented  with  serpents 
wreathing  about  their  heads  instead  of  hair  ; their  bodies  grew  indisso- 
lubly together,  and  their  very  looks  had  the  poxver  of  turning  into  stone 
all  those  on  whom  they  fixed  their  eyes.  Being  equipped  by  the  gods, 
he  mounted  into  the  air,  conducted  by  Minerva,  and  came  upon  the 
monsters,  who,  with  the  watchful  snakes,  were  asleep,  and  with  one 
blow  cut  off  her  head.  Perseus  then  made  his  way  through  the  air, 
with  Medusa’s  head  yet  bleeding,  in  his  hand,  and  from  the  blood 
which  dropped  from  it  as  he  flew,  sprang  all  those  innumerable  ser- 
pents that  have  ever  since  infested  the  sandy  deserts  of  Lybia.] 

Triangulum,  the  Triangle. — This  is  a small  constellation 
southwest  from  Medusa’s  Head,  in  the  constellation  Perseus.  It  may 
be  known  by  three  stars,  which  form  a triangle.  This  constellation  is 
of  recent  origin.  , 

Aries,  the  Ram. — This  constellation  lies  to  the  southwest,  about 
30®  from  the  zenith,  and  may  easily  be  distinguished  by  three  bright 
stars  in  the  head  of  the  Ram,  and  nearly  in  a right  line.  This  constel- 
lation twenty-two  centuries  ago  occupied  the  first  sign  in  the  ecliptic  ; or 
at  that  time  the  constellations  of  the  zodiac  and  the  signs  of  the  ecliptic 
corresponded  to  each  other  : but  in  consequence  of  the  retrograde  mo- 
tion of  the  equinoxes,  50"  a year,  the  constellations  of  the  zodiac  and 
the  signs  of  the  ecliptic  have  been  separated  from  each  other,  by  the 
falling  back  of  the  signs  in  the  ecliptic  about  31  degrees  : so  that  the 
constellation  Aries  is  now  in  the  sign  Taurus  of  the  ecliptic  ; and  Tau- 
rus in  Gemini,  and  Gemini  in  Cancer;  and  so  on.  This  constellation 
probably  received  its  name  from  the  Chaldean  Shepherds,  who  were  in 
those  days  the  best  astronomers,  from  the  fact  that  their  occupation  led 
them  to  be  on  the  watch  during  the  night,  to  defend  their  flocks  from 
the  ravages  of  w’ild  beasts.  They  observed  that  when  the  sun  entered 
this  division  of  the  heavens  the  lambs  were  with  their  flocks,  or  that  it 
was  the  season  for  the  increase  of  their  flocks — hence  the  Ram  was 
very  appropriately  made  to  represent  this  sign. 

Taurus,  the  Bull. — This  constellation  is  south,  about  30°  from 
the  zenith,  and  will  be  easily  distinguished  by  the  star  Aldebaran,  of 
the  first  magnitude,  situated  in  the  Bull’s  eye.  There  are  two  very 
important  clusters  in  this  constellation,  the  Hyades  on  the  head,  and 
the  Pleiades  on  the  neck  of  the  Bull.  This  constellation  probably 
derived  its  name,  as  well  as  the  other  signs  of  the  zodiac,  from  some 
particular  'phenomenon  which  was  apparent  at  that  particular  time.  It 


was  intended  to  show  that  this  was  the  season  for  the  increase  of  the 
ox  specie.s — hence  the  name  Taurus,  or  Bull. 

Gemini,  the  Twins, — This  constellation  is  situated  a little  to  the 
south  of  east,  and  may  be  known  Ijy  two  stars  of  the  2d  magnitude,  one 
in  each  head  of  the  Twins — their  names  («)  Castor  and  (j?)  Pollux. 
This  sign  was  originally  represented  by  two  goats,  and  was  probably 
intended  to  indicate  the  season  for  the  multiplication  of  this  animal,  as 
well  as  tt,  show  that  there  were  usually  two  at  a birth. 

Cancer,  the  Crab, — This  constellation  is  next  east  of  Gemini. 
It  contains  stars  only  of  the  4th  magnitude.  It  was  observed  by  the 
Ancients,  that  the  sun,  when  it  enters  Cancer,  passes  sideway  along 
the  tropic,  without  crossing  it,  w'hich  was  fitly  represented  by  a crab, 
which  moves  sideways. 

Orion. — This  constellation  is  southea.st  of  Taurus,  and  is  one  of  the 
most  conspicuous  constellations  in  the  heavens.  It  contains  two  stars 
of  the  first  magnitude.  (Note, — See  description  of  Map  No.  1.) 

Canis  ivtinor,  the  Little  Dog. — This  constellation  is  south- 
east of  Gemini.  It  contains  one  star  of  the  first  magnitude,  Procyon, 
and  one  of  the  3d,  Mirza,  in  the  head  of  the  Dog. 

Canis  Major,  the  Great  Dog. — This  constellation  is  situated 
to  the  southeast,  and  near  the  horizon.  The  principal  star  is  Sirius, 
the  brightest  star  in  the  whole  heavens.  (Note. — See  explanation  to 
Map  No.  1.) 

Lepus,  the  Hare. — This  constellation  is  south  of  Orion.  It  con- 
tains three  stars  of  the  3d  magnitude.  It  is  situated  west  of  the  Great 
Dog,  which  seems  to  be  pursuing  it  from  east  to  west,  owing  to  the 
motion  of  the  earth  on  its  axis.  The  hare  is  one  of  those  animals 
which  Orion  delighted  in  hunting,  and  for  this  reason  was  made  into  a 
constellation,  and  placed  near  him,  among  the  stars. 

Eridanus,  the  River  Po.— This  constellation  occupies  a large 
space  in  the  heavens  directly  south  of  Taurus.  It  will  lie  found  difli- 
cult  to  trace  it,  in  all  its  windings.  Its  entire  height  is  130  degrees. 
It  commences  near  the  star  Rigel,  in  the  foot  of  Orion.  Eridanus  is 
the  name  of  a celebrated  river  in  Italy,  now  known  by  the  name  of  the 
river  Po. 

Cstus,  th6  \^hale. — This  constellation  occupies  the  largest 
space  of  any  in  the  heavens,  and  is  west  of  the  River  Po.  As  the 
whale  is  the  chief  monster  of  the  ocean,  so  is  it  the  largest  constella- 
tion in  the  heavens.  It  is  considered  to  be  the  famous  sea  monster 
sent  by  Neptune  to  devour  Andromeda,  because  her  mother,  Cassio- 
peia had  boasted  herself  fairer  than  Juno,  or  the  sea  nymphs — but  was 
slain  by  Perseus,  and  placed  among  the  stars,  in  honor  of  his  heroic 
deeds. 

Monoceros,  the  Unicorn. — This  constellation  is  east  of  Orion, 
and  was  made  out  of  the  unformed  stars  of  the  ancients,  which  lay  scat- 
tered over  a large  space  between  the  two  dogs  Canis  Major  and  Canis 
Minor.  The  Monoceros  is  a species  of  Unicorn  or  Rhinoceros.  It  is 
about  the  size  of  a horse,  with  one  horn  growing  out  of  the  middle  of 
its  forehead. 

Columba,  the  Dove. — This  constellation  is  south  of  the  Lepus, 
The  Hare.  It  is  so  near  the  horizon  that  it  probably  will  not  be 
visible.  It  was  introduced  among  the  constellations  by  Rogu  in  1679. 

Camelopardalus,  the  Giraffe. — This  constellation  was  formed 
by  Hevelius,  in  the  beginning  of  the  17th  century.  It  was  made  up 
of  stars  not  included  in  the  adjacent  constellations,  viz:  Perseus,  Au- 
riga, the  head  of  Ursa  Major,  and  the  Pole  Star. 


i 

I 

I 

4 


74  ILLUSTRATED  ASTRONOMY. 


MAP,  FROM  NOVEMBER  1 TO  JANUARY  20. 

[0®*"  'I'he  Stars  and  Constellations  upon  this  Map  will  occupy  the  exact  positions  in  the  heavens  as  lliey  are  laid  dfiwri 
on  the  Map,  at  the  times  for  observations,  as  specified  in  tlie  table.  'I'he  centre  of  tlie  Map  represents  tlie  zenith  of  New- York, 
or  any  place  situated  upon  the  parallel  of  latitude  of  41°  north.  There  will  he  nine  stars  of  the  first  magnitude  above  the  hori- 
zon. The  star  Vega,  in  the  Harp,  being  so  near  the  northern  horizon,  may  not  be  visible.  'J’here  will  be  several  of  the  most 
conspicuous  constellations  in  the  whole  heavens  visible,  as  well  as  a considerable  number  of  stars  of  the  fiist  magnitude.  'J’he 
principal  constellations  arc  Auriga,  Taurus,  Orion,  Cants  IMajor,  and  Canis  Minor.  'J'his  is  the  best  season  for  observa- 
tion during  the  year,  as  the  atmosphere  is  generally  more  clear  than  at  any  other  time,  and  the  stars  twinkle  with  a beautiful 
brilliancy.] 


STARS  OP  THE  FIRST  MAGNITUDE. 


names  of  the  OONSTELLATICNS  and  PRINCIPAIi  STARS. 

AURIGA,  The  Charioteer — (Oapella  the  principal  star.) — 
This  star  is  about  15®  northeast  of  the,  zenith. 

TAURUS,  The  Bull— (Aldebaran.)— This  star  is  in  the  Bull’s 
Eye,  and  is  situated  about  25°  south  of  the  zenith,  and  5°  east  of  the 
meridian. 

CYGXUS,  The  Swan — (Deneb.) — This  star  is  situated  in  the 
Milky  Way,  and  west  of  the  North  Star,  about  midway  to  the  horizon. 

LYRA,  The  Harp — (Vega.) — This  star  is  northwest  of  the  North 
Star  and  elose  to  the  horizon — probably  not  visible. 


ORION,  Orion — (Betelgeuse.) — 'I'liis  star  is  in  the  right  shoul- 
der of  Orion,  and  situated  southeast  al)out  55  degrees. 

“ (Rigel.) — This  star  is  on  the  left  foot  of  Orion,  southeast  from 
Betelgeuse. 

CANIS  MAJOR,  Great  Dog — (Sirius.) — This  star  is  situated 
southeast,  about  20  degrees  above  the  horizon. 

CANIS  MINOR,  Little  Dog — (Procyon.) — This  star  is  south- 
east, and  about  40  degrees  above  the  horizon.  It  is  nearly  north  of 
Sirius. 

LEO  M.\J0R,  Great  Lion — (Regulus.) — This  star  is  nearly 
east,  and  about  15°  above  the  horizon. 


TABLE  OF  THE  TIMES  FOR  OBSERVATIONS 


SHOWING  THE  DAY  AND  HOUR  OF  THE  NIGHT  WHEN  THE  STARS  OCCUPY  THE  POSITIONS  INDICATED  ON  THE  MAP. 


H. 

M. 

H. 

31. 

H. 

M. 

n. 

M 

NOVEMBER. 

. 1 

1 

28 

NOVEMBER 

24 

11 

56 

DECEMBER 

17 

10 

24 

JANUARY.. 

. 9 

8 

56 

2 

1 

24 

25 

11 

52 

18 

10 

20 

10 

8 

52 

.5 

1 

20 

26 

11 

48 

19 

10 

16 

11 

8 

48 

4 

1 

16 

27 

11 

44 

20 

10 

12 

12 

8 

44 

5 

1 

12 

28 

11 

40 

21 

10 

8 

13 

8 

40 

6 

1 

8 

29 

11 

36 

22 

10 

4 

14 

8 

36 

7 

1 

4 

30 

11 

32 

23 

10 

— 

15 

8 

32 

8 

1 

— 

DECEMBER 

1 

11 

28 

24 

9 

56 

16 

8 

28 

0 

12 

56 

2 

11 

24 

25 

9 

52 

17 

8 

24 

10 

12 

52 

3 

11 

20 

26 

9 

48 

18 

8 

20 

11 

12 

48 

4 

11 

16 

27 

9 

44 

i9 

8 

16 

12 

12 

41 

5 

11 

12 

28 

9 

40 

20 

8 

12 

15 

12 

40 

6 

11 

8 

29 

9 

38 

21 

8 

8 

14 

12 

56 

7 

11 

4 

30 

9 

32 

22 

8 

4 

15 

12 

52 

8 

11 

— 

31 

9 

2S 

23 

8 

— 

10 

12 

28 

9 

10 

56 

JANUARY... 

1 

9 

28 

24 

7 

56 

17 

12 

24 

10 

10 

52 

.... 

2 

9 

24 

25 

7 

52 

18 

12 

20 

1 1 

10 

48 

3 

9 

20 

26 

7 

48 

10 

12 

10 

12 

10 

44 

... 

4 

9 

16 

27 

7 

44 

20 

12 

12 

13 

10 

40 

.... 

5 

9 

12 

28 

7 

40 

21 

12 

8 

11 

It) 

36 

.... 

6 

9 

8 

29 

7 

36 

22 

12 

4 

15 

10 

32 



7 

9 

4 

30 

7 

32 

25 

12 

— 

— 

16 

10 

28 

1 

8 

9 

— 

31 

7 

28 

I 1.  L II  S r R A T !•:  DAS  ']'  R ()  N O M V 


PliOliLEAlS  I’EREOKMEi)  WITH  THE  TEIHiESTlilAE  (lEOliE. 


Pkoblkm  1. — To  find  the  Latitude  of  any  ^ivrn  place. 

Rule. — Bring  the  given  place  to  the  graduated  side  of  the  T)rnss 
meridian,  and  (he  d('gree  on  the  brass  meiidian  over  tlie  place  is  the 
latituile,  which  is  either  north  or  soiiih. 

Q.  What  is  (he  latitude,  of  New  York  7 
A.  AI)out  41  degnn's  north. 

Q.  Wh  at  places  have  no  latitude? 

A.  All  places  on  the  e(]nator. 

Q.  Find  the  latitinle  of  the  following  places  : — 


London, 
Edinburgh, 
Moscow, 
Algiers, 
Norfolk, 
Madras, 
Prague, 
'I'ripoli, 

Pkoblem  2. 


Philadelphia, 

Rome, 

Stockholm, 

Astoria, 

Aleppo, 

Madrid, 

Dantzic, 

Paris, 


Boston, 

Dul)lin, 

Quito, 

Cape  of  Good  Hope, 
Athens, 

Cape  Horn, 
'rencrilfe, 

Lima, 


Washington, 

Amsterdam, 

M(*xico, 

Halifax, 

Ispahan, 

Cairo, 

I iisbon, 
Vienna. 


-To  fnd  the  Longitude  of  any  given  place. 

Rule Firing  the  given  place  to  the  brass  meridian,  and  the  degree 

on  the  equator  under  the  l)rass  meridian,  is  llv;  longitude.  [Note, — I.on- 
gitude  is  reckoned  from  the  meridian  of  Greenwich.  180  degrees  east 
and  west.) 

Q.  What  is  the  longitude  of  New  York  ? 

A.  74  degrees  west. 

Q.  What  is  the  longitude  of  Pekin? 

A.  1 16  degrees  east. 

Q.  Find  the  longitude  of  the  following  places  ; — 

M'ashington,  Hartford,  Sandwich  Islands,  Gibraltar, 

Quebec,  Rhodes,  Calcutta,  Constantinople, 

Canton,  Havana,  Jerusalem,  Nankin, 

Pekin,  St.  Petersburgh,  Venice,  Berlin, 

Astoria,  Cape  Horn,  New  Orleans,  Rio  Janeiro. 


Problem  3. — To  f nd  any  place  whose  latitude  and  longitude  are 
given. 


Rule. — Bring  the  given  longitude  to  the  brass  meridian,  and  under 
the  given  latitufle  is  the  place  required. 

Q.  What  place  is  situated  in  seventy-four  degrees  west  longitude. 


and  41  north  latitude  ? 

A.  New  Y’ork. 

Q.  What  places  have  the  follow 
Lat.  42®  north,  Lon.  71°  west. 
Lat.  .53°  north,  Lon.  6®  west. 
Lat.  38®  north,  Lon.  9“  west. 
Lat.  46®  north,  Lon.  75°  west. 


ig  latitudes  and  longitudes  ? 

Lat.  34°  south,  Lon.  18°  east. 
Lat.  41°  north,  Lon.  72°  west. 
Lat.  39°  north,  Lon.  75°  west. 
Lat.  32°  north,  Lon.  81°  west. 


Problem  4. — To  fnd  all  those  places  that  are  m the  same  latitude 
or  longitude  as  a given  place. 

Rule. — Bring  the  given  place  to  the  brass  meridian  ; then  all  the 
places  under  the  meridian  have  the  same  longitude  ; turn  the  globe 
round,  and  all  places  which  pass  under  the  latitude  of  the  place  have 
the  same  latitude. 

Q.  What  places  have  nearly  the  same  longitude  as  New  York? 

A.  Albany,  Montreal,  Bogota. 

Q.  What  places  are  in  the  same  latitude  ? 

A.  Boston,  Madrid,  Naples,  Constantinople. 

Q.  What  places  have  the  same  longitude  and  latitude  as  the  follow- 
ing places  : — 

Washington,  London,  St.  Petersburgh,  Rome,  Cairo, 

New  Orleans,  Mexico,  Canton,  Calcutta,  Dublin? 

Problem  .5.-— 7’o  find  the  difcrence  of  Latitude  between  any  two 
places. 

Rule. — I'ind  the  latitude  of  each  place,  and  note  them  down  ; then 
if  IjfRh  places  are  on  the  same  sule  of  the  ecpiator,  subtract  the  less 
latitude  from  the  gniater : if  they  are  on  the  ojrposite  sides  of  the 
equator,  add  the  latitudes. 

Q.  What  is  the  difli-rence  of  laliliidt;  bfitween  New  York  and  London  ? 

A.  New  York  41"  north,  London  .51®  north;  difference  1U° 


Q.  What  is  the  diflcrcnce  of  latitude  between  Washington  and  Cane 
Horn  ? ^ ' 

A.  Washington  37"  north.  Cape  Horn,  50"  south.— Hum  93." 

Cf  I’ind  the  difference  of  latitude  betwt’cn  the  following  |)l;icea 

New  Orleans  and  (Quebec.  Mexico  and  Rio  Janeiro, 

Madrid  and  Cairo,  Pekin  and  Botany  Bay, 

Ht.  Petersburgh  and  Rome,  Ca|)(*,  of  Good  Hojxi  and  Cape  Horn. 

Problem  6. — lo  fnd  the  difference  of  longitude,  between  any  two 
places. 

Rule. — find  the  longitude  of  each  place,  and  note  them  down  ; then, 
if  both  places  are  east  or  west  of  the  meridian,  subtract  the  less  Ion- 
gitude  from  the  greater ; but  if  one  is  east  and  the  other  west  add  the 
longitudes. 

Q.  What  is  the  difference  of  longitude  between  New  York  and  New 
Orleans  ? 

A.  New  York  /4®;  New  Orleans  90°,  west— difli’rence  16  degrees, 

Q.  What  is  the  diflerence  in  longitude  between  Boston  and  Romo? 

A.  Boston  71"  west ; Rome  12°  east— sum,  83  degrees. 

If  the  sum  of  the  longitudes  exceed  180  degrees,  subtract  it  from  360 
degrees;  the  remainder  will  be  the  diflitrence  in  longitude;  as,  Astoria 
124"  west;  Pekin  IIG"  cast=240  : 360—240=120"  difference  in 
longitude. 

Problem  7. — The  hour  of  the  day  at  any  place  being  given,  to  fnd 
what  o'clock  it  is  at  any  other  place. 

Rule. — Bring  the  place  at  which  the  time  is  given  to  the  brass 
meridian  ; set  the  index  to  the  given  hour,  then  turn  the  globe  till  the 
|)roposcd  place  comes  to  the  meridian  ; the  index  will  point  to  the  hour 
required.  If  the  place  required  is  east  of  the  given  place,  it  is  later  ; 
if  to  the  west,  it  is  earlier, 

Q.  When  it  is  noon  at  New  Y'ork,  what  is  the  time  in  London  ? 

A.  4 o’clock  56  min. 

Q.  When  it  is  noon  at  YV’ashington,  what  is  the  hour  at 
New  Orleans,  Mexico,  Quebec,  Boston,  Astoria,  Pekin, 

Cape  Horn,  Rome,  St.  Petersburgh,  Moscow,  Canton,  Dublin? 
^V'hen  it  is  midnight  at  New  York,  what  is  the  hour  at 
Paris,  Cairo,  Calcutta,  St.  Helena,  Gibraltar,  Havana, 

Constantinople,  Mexico,  Astoria,  Nankin,  Tunis,  Cadiz  ? 

Problem  8. — The  hour  of  the  day  being  given  at  any  place,  to  find 
all  places  on  the  globe  where  it  is  then  noon,  or  any  other  given  hour. 

Rule. — Bring  the  place  to  the  brass  meridian  ; set  the  index  to  the 
hour  of  that  place ; turn  the  globe  till  the  index  points  to  the  other 
given  hour ; then  all  places  under  the  brass  meridian  will  be  the  places 
required. 

Problem  9. — To  find  the  Antceci  of  any  place. 

Rule. — Bring  the  place  to  the  brass  meridian,  and  find  its  latitude , 
then,  under  the  same  degree  of  latitude,  on  the  opposite  side  of  the 
equator  will  be  the  Antceci. 

Problem  10. — To  fnd  the  Periaeci  of  any  place. 

Rule. — Bring  the  given  place  to  the  brass  meridian,  and  set  the 
index  to  twelve  ; turn  the  globe  till  the  index  points  to  the  other  twelve, 
and  under  the  same  degree  of  latitude  will  be  the  Periceci. 

Problem  11. — To  find  the  Antipodes  of  any  place. 

Rule. — Bring  the  place  to  the  brsss  meridian,  and  find  its  latitude, 
set  the  index  to  twelve,  and  turn  the  globe  till  the  index  points  to  the 
other  twelve ; then  under  the  same  degree  of  latitude,  on  the  other  side 
of  the  equator,  will  be  the  antipodes. 

Problem  12. — To  find  the  distance  in  miles  between  any  two  places 
on  the  (jlobe. 

Rule. — Lay  the  quadrant  of  altitude  over  the  two  places,  so  that  the 
division  marked  0 will  bo  on  one  of  the  places,  and  it  will  show  the 
number  of  degrees  between  them  ; which,  multiplied  by  69^  will  give 
the  distance  in  miles. 

Problem  13. — To  find  the  Sun's  Longitude  or  place  in  the  EcUptic, 
and  his  declination,  in  any  given  month  or  day. 


I L L U S T R A 'I'  E D A S 'F  R O N O M A' . 


■77 


Rule. — Look  for  the  given  clay  in  the  circle  of  months  on  the  wooden 
horizon,  and  opposite  to  it,  in  the  circle  of  signs,  are  the  sign  and 
degree  in  which  the  sun  is  for  that  day.  Find  the  same  sign  and 
degree  in  the  ecliptic  on  the  surface  of  the  globe ; bring  the  degree  of 
the  ecliptic,  thus  found,  to  the  brass  meridian,  and  the  degree  of  the 
meridian  will  be  the  declination. 

Problem  14. — To  find  the  time  at  which  the  Sun  rises  and  sets  at  any 
place,  the  datj  in  the  year,  and  the  length  of  the  day  and  night  at  that 
place. 

Rule. — Raise  the  pole  (of  the  hemisphere  in  which  the  place  is  sit- 
uated) as  many  degrees  above  the  horizon  as  are  equal  to  the  latitude 
of  the  place  ; bring  the  sun’s  place  on  the  given  day,  to  the  meridian, 
and  set  the  index  to  12 : bring  the  sun’s  place  to  the  eastern  horizon, 
and  the  index  will  show  the  time  of  the  sun’s  rising  ; bring  the  sun’s 
place  to  the  western  edge  of  the  horizon,  and  the  index  will  show  the 
hour  of  setting.  Double  the  time  of  the  sun’s  setting,  and  the  length  of 
the  day  will  be  had  ; double  the  time  of  the  sun’s  rising,  and  the  length 
of  the  night  will  be  had. 

Problem  15. — To  find  the  length  of  the  longest  and  shortest  days  and 
nights  at  any  place  on  the  earth. 

Rule. — If  the  place  is  in  the  northern  hemisphere,  elevate  the  north 


pole  till  the  horizon  cuts  the  brass  meridian  in  the  degree  corres|iond- 
ing  to  the  latitude  of  the  place ; bring  the  first  degree  of  Cancer  to  the 
meridian,  and  set  the  index  to  12  ; find  the  sun’s  place  in  the  ecli|)tic, 
(by  problem  13,)  and  bring  it  to  the  eastern  edge  of  the  horizon,  and 
the  index  will  show  the  hour  of  the  sun’s  rising;  double  this  titne,  and 
it  will  give  the  length  of  the  longest  night.  I’ring  the  sun’s  jtlace  to 
the  western  edge  of  the  horizon,  and  the  index  will  show  the  Innir  of 
setting;  double  this  time,  and  you  will  have  lint  length  of  the  longest 
day  at  that  place.  If  the  place  is  in  the  southern  hemisphei'(',  elevate 
the  south  pole  to  correspond  with  tlie  latitude  of  the  place  ; bring  the 
first  degree  of  Capricorn  to  the  meridian,  and  proceed  as  above. 

Q.  What  is  the  length  of  the  longest  day  and  shortest  night  at  New 
A^ork  ? 

A.  Longest  day,  14  h.  56  min. ; shortest  night,  9 h.  4 min. 

Problem  16. — 'To  find  those  places  where  the  Sun  does  not  rise  or  set 
on  a given  day. 

Rule. — Find  the  sun’s  declination  on  the  given  day,  (b^'  prob.  13,) 
raise  the  pole  (nearest  to  the  sun’s  place,)  as  many  degrees  above  the 
horizon  as  are  equal  to  the  declination  ; turn  the  globe  rouncl  on  its 
axis,  and  at  all'  places  that  do  not  come  above  the  horizon  the  sun  does 
not  rise  on  that  day  ; and  at  all  places  around  the  other  pole  that  do 
not  pass  below  the  horizon,  the  sun  does  not  set  on  that  day. 


PROBLEMS  PERFORMED  WITH  TIE  CELESTIAL  GLOBE. 

Q.  What  stars  have  the  following  right  ascensions  and  declinations? 


[Xjatitude,  on  the  Celestial  Globe,  is  reckoned  90°,  either  north 
or  south,  on  circles  of  Celestial  Latitude,  which  are  at  right  angles  to 
the  ecliptic.  (See  Diagram,  page  55.) 

liOngitude,  on  the  Celestial  Globe,  is  reckoned  on  the  ecliptic, 
from  the  first  degree  of  Aries,  eastward,  round  the  globe. 

IDeclination,  is  reckoned  from  the  equinoctial,  either  north  or 
south. 

Right  Ascension,  is  reckoned  on  the  equinoctial,  from  the  first 
degree  in  Aries,  eastward,  round  the  globe.] 

Problem  1. — To  find  the  Right  Ascension  and  Declination  of  the 
Sun  or  a Star. 

Rule. — Bring  the  sun  or  star  to  that  part  of  the  brass  meridian 
which  is  numbered  from  the  equinoctial  towards  the  poles : the  degree 
on  the  brass  meridian,  over  the  place,  will  show  the  declination  ; and 
the  number  of  degrees  on  the  equinoctial,  between  the  brass  meridian 
and  the  first-  point  of  Aries,  is  the  right  ascension. 

Required — the  right  ascension  and  declination  of  the  following  stars  : 
Aldebaran,  in  Taurus,  j Arcturus,  in  Bootes, 

Sirius,  in  the  Great  Dog,  i Capella,  in  Auriga, 

Vega,  in  the  Harp,  | Regulus,  in  Leo. 

Problem  2. — To  find  the  Latitude  and  Longitude  of  a Star. 

Rule. — Place  the  end  of  the  quadrant  of  altitude,  which  is  marked 
90®,  on  the  north  or  south  pole  of  the  ecliptic,  according  as  the  star  is 
north  or  south  of  the  ecliptic ; then  move  the  other  end  till  the  gradua- 
ted edge  of  the  quadrant  comes  to  the  star.  The  number  of  degrees  on 
the  quadrant,  between  the  ecliptic  and  the  star,  is  the  latitude  ; and  the 
number  of  degrees  on  the  ecliptic,  reckoned  eastward,  from  the  first 
point  of  Aries  to  the  quadrant,  is  the  longitude. 

Example. — Required,  the  latitudes  and  longitudes  of  the  following 
stars  : — 

Aldebaran  in  Taurus.  Ans.  Latitude  5®  28'  S. ; longitude,  2 signs 
6®  53',  or  6®  53'  in  Gemini. 

Deneb,  in  the  Swan,  Altair,  in  the  Eagle, 

Antares,  in  Scorpio,  Rigel,  in  Orion, 

Fomalhaut,  in  the  S.  Fish,  Pollux,  in  Gemini. 

Problem  3. — The  declination  and  right  ascension  of  a Star,  the 
Moon,  a Phmet,  or  a Comet,  being  given,  to  find  its  place  on  the  globe. 

Rule  — Bring  the  given  degrees  of  right  ascension  to  that  part  of 
the  brass  meridian  which  is  numbered  from  the  equinoctial  towards  the 
poles ; then  under  the  given  declination  on  the  brass  meridian  you  will 
find  the  star  or  planet. 


Right  Ascension. 

Declination. 

Right  Ascension. 

Declination. 

76°  14' 

8°  27'  S. 

86°  13' 

44°  .55' N. 

83  6 

34  11  S. 

99  5 

16  26  S. 

25  54 

19  50  N. 

11  11 

59  38  N. 

.53  54 

23  29  N. 

1 46  32 

9 34  S. 

Problem  4. — 

■The  latitude  and  longitude  of  the  Moon,  a Star,  or 

Planet,  being  given,  to  find  its  place  on  the  globe. 

Rule. — Screw  the  quadrant  of  altitude  on  the  pole  of  the  ecliptic, 
and  place  the  other  end  on  the  given  degree  of  longitude  in  the  ecliptic ; 
then,  under  the  given  latitude,  on  the  graduated  edge  of  the  quadrant, 
you  will  find  the  star,  or  place  of  the  moon  or  planet. 

Q.  What  stars  have  the  following  latitudes  and  longitudes  ? 


Latitudes. 

16®>  3'  S. 
22  52  N. 
5 29  S. 
44  20  N. 


Longitudes. 

2®  25°  51' 
2 18  57 

2 6 53 

7 9 22 


Latitudes. 

10°  4'  N. 

21  6 S. 

12  3 S. 

0 27  N. 


Longitudes. 

3®  17°  21' 
11  0 56 

1 11  25 

4 26  57 


Problem  5. — The  latitude  of  a place,  the  day  and  hour  being  given, 
to  place  the  globe  in  such  a manner  as  to  represent  the  heavens  at  that 
time,  in  order  to  point  out  the  situations  of  the  constellations  and  remark- 
able stars. 

Rule. — Elevate  the  pole  for  the  latitude  of  the  place,  and  set  the 
globe  due  north  and  south  by  a meridian  line  ; find  the  sun’s  place  in 
the  ecliptic,  bring  it  to  the  brass  meridian,  and  set  the  index  to  12.  If 
the  time  be  afternoon,  turn  the  globe  westward  ; if  in  the  forenoon,  turn 
the  globe  eastward,  till  the  index  points  to  the  given  hour.  The  sur- 
face of  the  globe  then  represents  the  appearance  of  the  heavens  at  that 
time  and  place. 

Problem  6. — To  find  the  distance  of  the  Stars  from  each  other,  in 
degrees. 

Rule. — Lay  the  quadrant  of  altitude  over  any  two  stars,  so  that  the 
division  marked  0 may  be  on  one  of  the  stars  ; the  degrees  between 
them  will  show  their  distance,  or  the  angle  which  these  stars  subtend, 
as  seen  from  the  earth. 

Example. — What  is  the  distance,  in  degrees,  between  the  two  stars 
Vega  and  Altair  ? Ans.  34  degrees. 

Also,  between  Regulus  and  Procyon, 

“ “ Aldebaran  and  Sirius, 

“ , “ Arcturus  and  Spica, 

“ “ Capella  and  the  North  Star? 


78 


I I.  |i  S 'I'  11  A 'r  K I)  A H T 11  ()  N ()  M V . 


GLOSSARY, 

OR  EXPLANATION  OF  ASTRONOMICAL  TERMS, 


An  npporcnt  nnnnal  motion  in  the  fixed  Btora,  occasioned  by  tlic  velocity  of 
light  combined  with  tlie  real  velocity  of  tlie  cnrtli  in  its  orbit. 

Jibsorhent  Media  ^Substances  cither  solid,  liquid,  or  llu id.  wliich  imbibe  the  rays  of  Uglit  and  heat. 
^.Acceleration. — An  increase  in  tlie  ia])idity  of  the  motion  of  a moving  ho  ly  'I'lic  motions  of  the 
planets  are  accelerated  from  tlicii  aphehon  to  their  perihelion 
^dcronycaL^^.K  star  \h  said  to  rise  or  to  sot  acronycuUy  when  it  ri.ses  or  sets  at  the  instant  of  sunset. 
JF.tiform. — Having  the  form  of  air. 

JErolite. — A meteoric  stone. 

or  ^'Itmo^nhere.—A  transparent,  invisible,  clastic  fluid,  surrounding  the  earth,  in  which  we 
move  and  breathe. 

JiLtitude. — The  lieightofan  olijert  above  tlie  horizon. 

^dmphiscii. — A name  apjilied  to  the  inlialiitants  of  the  torrid  zone,  because  within  ti  e year,  their 
shadows,  at  noon,  are  cast  both  north  and  south 

^'lmj)litude.^T\\Q  distance  whicli  a heavenly  body  rises  from  the  east,  or  sets  from  tlie  west  point 
of  the  horizon 

*47ia/cw7«a.— A figure  on  the  artificial  globe,  drawn  from  one  tiopic  to  tlic  other,  on  whicli  is 
marked  the  sun’s  declination  for  each  day'  in  the  year. 

The  corner  or  opening  between  two  lines  tint  meet.  A right  angie  contains  ‘‘Odogrrea, 
and  is  formed  by  one  line  falling  iierpcndicularly  upon  another.  An  acute  orsliarp  angle  is  less 
than  a right  angle.  An  obtuse  or  blunt  angle  is  greater  than  a riglit  angle  The  measure  of  an 
angle  is  always  an  arc. 

An^le  of  Position  of  a Double  Star.^ThQ  angle  which  a lino  joining  the  two  stars  makes  with 
one  parallel  to  the  meridian. . 

^An'’xdar  Distance.— '\'\\o  distance  between  two  objects,  which  is  indicated  by  the  angle,  made  by 
straight  lines  drawn  to  them  from  a given  point. 

Jinniial  Equation  —A  periodical  inequality  in  the  motion  of  the  moon,  or  a ]danct,  going  through 
its  changes  in  a year. 

^Annual  Revolution  of  the  Earth. — Its  yearly'  revolution  round  the  sun. 

^Annular. — Having  tlic  form  of  a ring. 

^Anomaly. — The  sun's  angular  distance  from  the  apogee,  or  the  earth's  from  aphelion. 

^inlaictic  Circle  — Circle  round  the  south  pole,  **3'’  ‘iS’  from  it 
•.Antipodes. — I hose  wlio  live  on  directly  opposite  sides  of  the  earth. 

Jintaci. — Tliose  who  live  in  equal  latitude  on  directly  opposite  sides  of  tlie  equator. 

•.Aphelion. — The  point  in  a planets  orbit  which  is  fartlic.U  from  the  sun. 

•.Apogee. — The  point  of  the  orbit  of  the  moon  or  a planet  farthest  from  the  earth. 

•.Apparent  Diameter  — The  diameter  of  a body’  as  seen  from  the  earth. 

•Apparent  Motion. — The  motion  of  the  lieavenly  bodies  a.s  viewed  from  the  earth. 

Jlpparent  Time. — The  lime  shown  by  the  sun,  as  indicated  by  a dial. 

•Apsis. — llie  point  of  an  orbit  which  is  at  the  greatest  or  least  distance  from  the  centre  ot  motion. 
The  former  is  called  the  higher  apsis  ; the  latter  the  lower  apsis  The  two  together  are  termed  the 
apsides,  and  a line  uniting  them  is  called  the  apsis  line,  or  line  of  tho  apsides. 

•Aquarius. — The  eleventh  sign  of  the  ecliptic. 

Anv  part  of  the  circumference  of  a circle. 

•Arctic  Circle  — A circle  roun  1 the  north  pole,  OS'  from  it. 

•Areas. — In  astronomy,  they  ar»»  the  spaces  passed  over  by  the  radius  vector  of  a celestial  body. 
•Aries. — Tlie  first  sign  of  the  ecliptic.  Its  first  point  is  at  the  vernal  equinox. 

•irgumeTTt. — A quantity'  by  which  another  quantity  or  equation  is  found. 

•Ascensional  Difference. — 'I'he  diflerence  between  right  and  oblique  ascension 
•Aspect. — The  appearance  of  the  heavenly  bodies  with  respect  to  position,  angular  distance.  &c. 
•Asteroids. — Eight  small  jirimary  planets,  who.se  orbits  are  between  those  of  Mars  and  Jupiter. 
Their  names  are  Vesta.  Astraea.  Juno,  Ceres,  Pallas,  Hebe.  Iris  and  Flora.  Some  suppose  them  to 
be  fragments  of  a planet,  burst  by  some  internal  explosion. 

•Astronomical  Time  — 7’ime  reckoned  from  the  noon  of  one  day  up  to  24  hours,  to  the  noon  of 
the  next  day.  It  con.sequently’  is  made  up  of  the  last  12  hours  of  the  same  civil  day,  and  the  first 
12  hours  of  the  next  civil  day. 

•Atmosphere  — The  air  that  surrounds  the  earth 

•Attraction — The  power  of  one  body  to  draw  another  towards  it. 

•Austral. — Southern. 

•Aurora. — The  morning,  or  the  morning  twilight. 

•Aurora  Borealis,  or  Xorthem  Lights  — A luminous  appearance  in  the  heavens,  usually  seen  in 
high  latitudes,  and  so  named  from  its  frequent  resemblance  to  the  morning  dawn. 

•Axis  of  Rotation. — The  line  around  whicli  a revolving  body  turns. 

•Axis  of  an  Ellipse. — The  major  axi.s  is  the  greatest  diameter.  Tho  minor  axis  is  the  least 
diameter. 

•Azimuth. — The  distance  of  a heavenly  body  east  or  west  of  the  meridian,  which  is  indicated  by 
the  angle  between  the  meridian  and  the  vertical  circle  passing  through  the  body 
•Azimuth,  or  I'ertical  Circle  — A great  circle  in  the  heavens,  passing  through  the  zenith  and  nadir, 
and  cutting  the  horizon  at  right  angles. 

Binary  System  of  Stars. — Tw’o  stars  revolving  about  each  other. 

Bissextile,  or  Leap  year. — Rlvery  fourth  yar.  in  which  February  has  29  days. 

Body. — In  astronomy  this  term  is  applied  to  any  one  of  the  celestial  orbs. 

Calendar. — A term  applied  to  the  Almanac,  or  the  divisions  of  time  of  which  it  treats. 

Calendar  Months. — The  months  as  laid  down  in  the  almanac. 

Cancer. — The  fourth  sign  of  the  eclijitic. 

Cajmeam.—Tha  tenth  sign  of  the  ecJii)lic. 

Cardinal  Points. — The  east,  west,  north  and  south  points  of  the  horizon 

Centrifugal  Force. — The  force  which  urges  a revolving  body  forward  in  Its  orbit,  or  tends  to 
carry  it  away  from  the  centre  of  motion. 

Centripetal  force  — The  force  which  draws  a revolving  body  towards  the  centre  of  motion. 

Chord  — A straight  line  from  one  end  of  an  arc  to  the  other. 

Circle.  — h figure  bounded  by  a curve  line,  every  part  of  which  is  equally  di.^tant  from  the  cen- 
tra. A great  circle  is  one  whose  plane  divides  a globe  into  two  equal  parts  called  hemispheres  ; 
% small  circle  is  one  whose  plane  divides  a globe  into  unequal  parts. 

Circle  of  Declination  —The  circle  where  tlic  piano  of  the  meridian  meets  the  heavens. 

Cinle  of  HhiminaaVn.— The  circle  that  divides  the  euliglilMicd  from  the  ilark  licniisphere. 
Circuinferen'e—Th^  bourvJary  of  a circle.  The  circumference  of  every  circle  is  supposed  to  bo 
divided  into  equal  parts,  called  degrees  ; each  degree  into  W)  equal  parts,  called  minutes  ; and 
each  minute  into  *>0  equal  j*art»,  called  seconds. 

Circumpolar  .Star# —Those  stai*  w'liich  revolve  around  the  pole  witliout  passing  below  the 
horizon 

Clouds  -Vapor,  in  the  a»mospljcrc,  condensed  into  small  drops  of  water,  and  thus  rendered 
visible  , , » . . 

Colures  7 hose  two  meridians  which  pass  through  tlic  equinoctial  and  solstitial  points  of  the 
ecJiiitic.  called  t!.e  cquinortial  and  soh.titial  cobires 

Comet  -A  body  with  a lurninouN  (rain  or  tail,  moving  around  the  sun  in  a very  elongated  orbit. 
Compteinenl  of  an  Jlrt  or  .Ancle  What  it  wants  of  90  degrees. 

Con'at  e Ibdiovring  in  a circular  manner 
Cimfeutne  (titflrs.  Mr'  les  having  the  same  centio 

(‘one  A solid  with  0 circular  ha^e,  imd  tapering  equally  upwards  to  a point. 

(Jimj$inttion  7 wo  heavenly  hodieg  are  in  conjunction  when  they  have  the  same  longitude.  A 
planet  Is  in  Inferior  con. unction  when  it  is  between  theciith  and  sun  ; in  superior  conjunction  when 
It  II  iteyond  ttio  son  7 he  inferior  planets  only  have  inlerior  conjunction,  hut  all  havu  superior  con- 

^ ^Oonstelhilions  ^/roMps  of  sisrs  to  which  tlie  iiarnev  of  men  and  iinlrnals  were  anciently  given. 
71(S  vriioln  starry  f»rmam«nl  Is  divided  Into  :iucli  gioiqis. 


Ccnrcj’.— Rounding  out  in  a circular  manner. 

C<>#7»tcrt/  - i he  rising  or  setting  ol  a sl.ir  is  said  to  ho  cosrnical,  when  it  ri«es  or  sets  nt  trio 
moment  of  sun^l^c. 

Cube.  A square  solid  ol  six  equal  sides 

Culminate.  'I’o  jiass  the-  highest  point  of  the  diurnal  air,  which  is  nt  the  meridian. 

Cuhniiuition  — 7*l»e  passing  over  tlie  meridian,  or  point  of  liigliest  altitude 

Cprle.—A  pcrioil  of  lime  in  which  the  same  phenomona  or  circuinstnnrei  of  a body  begin  to  occur 
again  in  tlie  same  order 

Cycle  of  the  Moon,  or  Metonic  Cycle  \ period  of  19  years  ; after  which  the  changes  of  tho  moon 
return  to  tlie  same  days  of  the  month  (when  five  leap  years  arc  included,)  as  on  the  same  lear  of 
the  preceding  cycle,  or  19  )enrs  helore. 

Cijilc  of  (he  Sun  A period  of  2y  years  ; after  wliich  tlie  same  ilays  of  the  month  return  f»i  the 
same  days  of  the  week  ; an«!  the  sun’s  pl.icc,  to  the  same  degrees  and  miiiiites  uX  the  eirh|.(M'  uk  on 
tho  same  ) ear  of  the  preceding  cycle. 

Cycle  of  a Planet.— .\  period  during  which  a planet  passes  through  its  various  positions  with 
roNnccl  to  the  sun  and  earth. 

Cylinder. — A round  figure  or  solid  of  equal  si/c  from  end  to  end. 

Cylindrical. — Having  llic  form  ol  a cylinder 

Declinalion.—  rho  angular  distance  of  a lieavenly  body,  north  or  south,  fiorn  the  cquinortial 
Degree — One  3h0lh  pailof  the  Circumference  ol  a circle. 

Diagonal. — A line  dtawn  from  corner  to  corner  of  a four  sided  figure 
Dial.— An  iiHtrumcnt  showing  the  hour  ol  tlie  day.  by  the  shadow  of  tho  sun 

Diameter —A  straight  line  jmssing  through  the  centre  of  a figure,  and  terminated  both  ways  liy 
its  sides  or  surface.  7'ho  longest  and  shorle^l  diameters  of  an  i-llijise  arc  callcfl  the  transverse  and 
conjugate  diameters 

Dichotomized  —Diuded  into  equal  and  similar  parts,  as  the  disc  of  the  moon  at  qnadratirro. 

Digit. — One-twelflh  part  of  tho  apparent  diameter  of  the  sun  or  moon 

Direct  motion  of  a Planet motion  from  west  to  cast,  according  to  the  order  of  the  signs. 
Disc. — 'J’lie  apparent  surface  of  a hcHvenly  body. 

Diurnal  •Arc.— The  arc  described  by  a lieavenly  body  from  its  rising  to  its  setting. 

Diurnal  Revolution  of  the  Earth.  Its  daily  rotation  on  its  axis,  from  west  to  east. 

Dominical  Letter.— Thu  letter  in  the  calendar  against  Sunday  ; the  first  7 letters  of  the  alphabet 
being  applied  to  the  first  7 days  of  tlic  year. 

Dionysian  PtHod  - A period  of  >32  years ; found  by  multi])lying  tbe  cy.  Ics  of  the  sunand  moon. 
Earth  — 7'he  globe  on  which  wc  live. 

East. — The  direction  in  which  the  sun  rises  at  the  equinoxes. 

EccentHc. — Deviating  from  the  centre  ; inegnlar. 

EcccentHc  Circles  — U hose  that  arc  wliolly  or  partially  included  in  each  other,  but  have  difli.-rent 
centres. 

Eccenhicity. — 7'he  distance  from  the  centre  of  an  ellipse  locitherof  its  foci. 

Ecliptic. — The  circle,  where  the  plane  of  tlic  earth's  orbit  meets  the  heavens. 

Egress  — The  act  of  going  out 

Element. — Fundamental  principle  ; quantity  by  which  something  else  is  found. 

Elevation  — Height  or  altitude 

Ellipse. — An  oval ; a figure  made  by  the  oblique  section  of  a cone. 

Elongation. — 'I'lie  angular  distance  of  a planet  from  the  sun,  or  the  dilfcrence  of  their  celestial 
longitude. 

Exnersion. — The  act  of  rising  out  of  something,  or  rc-appcaring. 

Epact  — The  age  of  the  moon  at  the  commencement  of  the  year. 

Epicycle. — The  curve  described  by  a point  of  one  circle,  revolving  upon  another  circle 
Epoch  or  Era. — A particular  time,  from  which  events  arc  reckoned. 

Equation. — A quantity  to  be  applied  to  mean  time,  place,  or  motion,  in  order  to  find  the  true. 
Equator. — A great  Circle,  whose  plane  is  perpendicular  to  the  earth’s  axis. 

Equinoctial  or  Celestial  Equator. — The  circle,  where  the  plane  of  the  equator  meets  the  heavens. 
Equinoctial  The  points  where  tlie  equinoctial  cuts  the  ecliptic,  or  the  first  points  of  Ar.es 

and  Libra. 

Equinox. — The  time  wdien  the  sun  enters  either  of  the  equinoctial  points.  The  vernal  equinox 
occurs  in  March,  the  autumnal  in  September. 

Evection — A periodic  inequality  in  the  motion  of  the  moon. 

Fh-mament. — The  heavens,  or  orb  of  fixed  stars. 

Fixed  Stars. — Those  stars  which  preserve  the  same  situation  with  respect  to  each  other. 
f'oci, — The  plural  of  focus  ; the  two  points  round  which  an  ellipse  is  drawn. 

Fogs  or  Mist  — Vapor,  condensed  into  minute  drops  of  water,  as  in  clouds. 

Fi'ustum. — What  remains  of  a regular  figure  after  a piece  is  cut  oft' by  a plane  parallel  to  its  base 
Galaxy  or  Milky  Way. — A luminous  zone  in  the  heavens,  composed  of  an  immense  number  of 
fixed  stars 

GeocentiAc. — As  seen  from  the  earth,  or  the  earth  being  the  centi-e. 

Gibbous  — The  shape  of  the  illuminated  part  of  the  moon,  when  more  than  half  and  not  the  whole 
of  its  disc  is  visible. 

Globe. — A sphere,  ball,  or  round  body.  Artificial  globes  of  tw’o  kinds  are  made  ; the  terrestial, 
to  represent  the  earth  ; and  the  celestial,  to  represent  the  heavens. 

Golden  Number. — The  number  of  years  in  the  cycle  of  the  moon  since  the  epact  was  nothing. 
Gravitation  or  Gravity. — The  attraction  or  pow'er  which  draws  all  bodies  towards  each  other. 
Also,  its  eft'ect.  as  weight,  caused  by  the  earth’s  attraction. 

Hail. — Drops  of  rain,  frozen  while  falling 

Haivest  Moon. — 7'he  full  moon  nearest  the  autumnal  equinox. 

Heliacal. — The  heliacal  rising  or  setting  of  a star  takes  place,  when  it  rises  a little  before  or  sets 
a little  after  the  sun. 

Heliocentric. — As  seen  from  the  sun,  or  the  sun  being  the  centre. 

Hemisphere. — Half  a sphere  or  globe. 

Heteroscii. — A name  given  to  the  inhabitants  of  the  two  temperate  zones,  because  at  noon  those 
in  the  northern  always  have  their  shadows  in  an  opposite  direction  to  those  in  the  souihem 

Ilonzon  — The  visible  or  sensible  horizon  is  the  circle  w’hero  the  sky  and  earth  appear  to  meet. 
The  rational  horizon  is  parallel  to  the  visible,  and  its  plane  divides  the  earth  into  upper  and  lower 
licmispheres.  It  is  represented  on  the  artificial  globe  by  the  wooden  horizon.  The  circle  W’here 
its  plane  meets  the  heavens  is  called  the  celestial  horizon. 
llonzontal. — Level  or  iiarallcl  to  the  horizon 

Hour  Circle. — A small  circle,  on  the  globe,  near  the  north  pole,  having  on  it  the  hours  of  the  day. 
Immersion. — I'he  act  of  plunging  into  something,  or  disappearing. 

Inclination — .Angle.  A position  forming  an  acute  angle- 

index. — A movable  hand  on  the  globe,  to  point  out  the  lime  on  the  hour  circle. 

Ingress. — .-Vn  entrance 

Intercalation. — The  insertion  of  an  extra  day  in  the  calendar,  ns  tho  Bissextile. 

Julian  Period.— .\  period  of  7,980  years,  found  by  multiplying  together  the  cycles  of  Ih#'  sun  and 
moon,  and  the  Homan  Indiction. 

Julian  Vear.—A  jicriod  ofcxactly  365]  days. 

Latitude  on  the  Earth.— Tho  distance  of  a place  north  or  south  of  the  equator 
iMtitude  in  the  Heavens. — 7'lu‘  angular  distance  of  a heavenly  body  from  the  ecliptic. 

Leap  Year. — Every  fourth  year,  in  whicli  an  extra  day  is  added  to  tho  calendar 
Lro,— 7'he  fifth  sign  of  the  ecliptic. 

Libra  —7'ho  7th  sign  of  the  cclintic. 

Lihradon  of  (he  Monn.—.\  periodical  oscillation  of  her  disc. 

J,ijnh.—T\\Q  cnrvcil  edge  of  the  sun  or  moon’s  disc. 

7.i7i«.— 7'hat  which  lia.s  length  hut  no  breadth. 

Longitude  on  the  Earth.— DmUuu'c  east  or  west  of  llio  first  meridian. 


If.  1.  U S 'I'  11  A T K D A S T R O N ()  M Y 


70 


GLOSSARY,  OR  EXPLANATION  OF  ASTRONOMICAL  TERMS,  (continued.) 


Ltm^Uudt  in  the  Heavens. — The  angular  distance  of  a heavenly  body,  measured  on  the  ecliptic 
eastward,  Irom  the  first  point  of  Aries. 

Xummouj.— Capable  of  shining  without  light  from  anotlier  body. 

Lunar  Distance. — The  angular  distance  ol  the  centre  of  a celestial  object  from  the  centre  of  tlio 
moon. 

Lunar  Month. — The  time  from  one  new  moon  to  the  next. 

Lunation. — The  average  time  of  the  lunar  month 

Mariner's  Oumpass. — An  instrument  with  a magnetic  needle,  to  point  out  the  horizontal 
direction. 

Mass. — The  quantity  of  matter  in  a body. 

Mean. — Average  ; applied  to  distance,  longitude,  motion,  place,  time,  &c. 

Mendian  of  a Place. — A great  circle  passing  through  the  place  and  tlie  poles  of  the  eai  th.  The 
first  meridian  is  the  one  from  which  longitude  is  reckoned.  The  brazen  meridian  is  that  in  which 
the  artificial  globe  turns. 

Meteor. — A transitory  object  in  the  air.  Falling  stones  are  often  called  meteorites 
Minute. — One  60th  part  of  a degree  ; also  one  GOth  part  of  an  hour. 

Moon's  Southing. — The  time  when  the  moon  comes  to  the  meridian  of  a place. 

Nadir. — A point  directly  opposite  to  the  zenith,  or  beyond  tiie  centre  ol  the  earth. 

Neap  Tide. — 'I'he  least  flood  and  ebb  tide. 

I^lehula. — CIu8-«''rs  of  Stars,  or  other  causes  of  the  luminous  appearances  in  tlie  heavens. 

Noctuj'nal  Arc.  The  arc  described  by  a heavenly  body  from  its  setting  to  its  rising. 

Nona^esimal  Decree. — The  highest  point  of  the  ecliptic  above  the  horizon. 

Node  — The  point  of  the  moon's  or  a planet’s  orbit  that  is  cut  by  the  plane  of  the  ecliptic.  There 
are  two  nodes,  one  on  eacli  side  of  the  centre  of  motion  ; and  a line  joining  them  is  called  the  line 
of  the  nodes.  7'he  jilace  wheie  the  body  passes  to  the  north  of  the  ecliptic  is  called  the  ascending 
node  \ the  other  the  descending  node. 

New  Style. — The  reckoning  of  time  established  by  Gregory  XIII.,  and  now  generally  adopted. 
North — That  point  of  the  horizon  which  is  directly  towards  tlie  northern  pole. 

Nucleus  of  a Comet. — The  uart  of  its  head  which  apjiears  to  be  dense. 

Nutaiion  — A variation  in  the  direction  of  the  earth’s  axis,  caused  by  the  attraction  of  the  moon 
on  the  protuberant  matter  at  the  terrestrial  equator 

Ohlique-  'Forming  an  acute  or  obtuse  angle  ; not  perpendicular. 

Ohliyue  Ascension. — That  degree  of  the  equinoctial  which  rises  with  a body  in  an  oblique 
sphere. 

Ohliyue  Descensioii. — That  degree  of  tho  equinoctial  which  sets  with  a body  in  an  oblique 
spliere. 

Obliquity. — Deviation  from  parallelism  anil  from  perpendicularity. 

Obliquity  of  the  Kcliptic. — I’he  an^le  formed  by  the  equinoctial  with  the  plane  of  the  ecliptic. 
Occidental. — To  the  west,  where  tlie  heavenly  bodies  appear  to  desceml. 

Occultation  — 'I'he  eclipse  of  a star  or  planet  by  tho  moon  or  by  another  planet. 

Octant. — Forty-five  degrees  distant,  or  the  eighth  part  ol  a circle. 

Old  Styl^^. — That  reckoning  of  time  which  makes  eveiy  fourth  year  a leap  year. 

Opakc. — Not  luminou.s  or  transparent 

Cy}>pos{tion — Two  bodies  are  in  opposition  w'hen  they  are  on  opposite  sides  of  the  earth. 

Orbit. — The  path  in  wliicli  one  body  moves  round  another. 

0^‘iental. — Towards  the  east,  where  tlie  heavenly  bodies  rise. 

Parallax. — The  difference  of  the  place  of  u body,  as  seen  from  different  points  of  view  Diurnal 
parallax  is  the  difierence  between  tiie  apparent  and  true  plac«  of  a body.  Horizontal  parallax  is 
the  diurnal  pnralla.K  of  a body  in  the  horizon.  .\TinuaI  parallax  is  the  difference  of  the  apparent 
place  of  a body,  as  seen  from  different  parts  of  the  earth's  orbit. 

Parallactic  Motion. — .Angular  motion  sufficiently  great  to  be  perceived. 

Parallel  Lines. — Those  continued  in  the  same  direction,  at  the  same  distance  from  each  other. 
Parallels  of  altitude,  declination,  and  latitude,  are  small  circles  parallel  to  the  horizon,  equinoctial, 
and  equator. 

Penumbra. — A partial  or  imperfe<rt  shadow. 

Pmgee  — The  point  nearest  the  cai  lh,  in  the  orbit  of  the  moon  or  a planet. 

Perioeci. — Those  who  live  in  equal  latitude  on  opposite  sides  of  the  pole. 

Pei'ihelion . — The  low'er  apsis,  or  point  nearest  the  sun,  in  a planet’s  orbit. 

Periodic  Inepiality  — An  irregularity  in  the  motion  of  a celestial  body,  requiring  a comparatively 
short  lime  for  its  accomplisliment. 

Periodic  Time  — The  time  in  which  a heavenly  body  revolves  around  its  centre  of  motion 
Ptriscii — A name  given  to  the  inhabitants  of  the  frigid  zone,  because  their  sliadows  turn  all 
round  them  in  one  day 

P<»j7>md/cu/ar.— Making  a right  angle  with  some  line  orsurfficc. 

Perturbations. — Irregularities  in  the  motions  of  bodies,  from  some  disturbing  cause. 

Phases  — Different  appearances  of  the  moon  and  planets  as  they  are  differently  illuminated. 
Phenomena. — .Appearances  in  the  works  of  nature.  (Singular  Phenomenou.) 

Physical. — Belonging  to  material  natuie. 

Pisces. — The  l-2th  sign  of  the  ecliptic. 

Plane. — Length  and  breadth  without  thickness.  The  plane  of  a circle  is  the  surface  contained 
within  it.  and  continued  out  of  it  on  all  sides,  indefinitely,  to  the  heavens. 

Planet — -An  opake  body  revolving  around  the  sun  The  secondary  planets  revolve  around  the 
primary  planets,  as  well  as  around  the  sun.  Those  planets  nearer  to  the  sun  than  the  eartli  is,  are 
called  inferior;  those  more  distant  are  called  superior. 

Pleiades. — The  seven  stars  in  the  constellation  Taurus. 

Potnb— That  which  has  position  but  no  magnitude. 

Polar  Circles  — Small  circles  drawn  around  the  poles,  23^  degrees  from  them. 

Polar  Distance. — .Angular  distance  from  the  pole,  measured  on  a circle  of  declination. 

Poles. — The  terrestrial  poles  are  the  extremities  of  the  eartli’s  axis.  The  celestial  poles  are  the 
points  where  the  cai  th’s  axis,  if  produced,  would  meet  the  heavens 

Pole  Star. — .A  star  of  the  second  magnitude,  near  the  north  pole  of  the  heavens. 

Pointers. — Two  stars  in  the  great  bear,  that  serve  to  point  out  the  pole  star 

Precession  of  the  Equinoxes. — A retrograde  motion,  on  the  ecliptic,  of  the  equinoctial  points, 
caused  by  the  action  of  the  sun  and  moon  upon  the  protuberant  matter  at  the  earth’s  equator. 
(luadrant. — Ninety  degrees,  or  a quarter  of  a circle.  An  instrument  to  measure  angles. 
Quadrature. — The  position,  a quarter  of  a circle  from  the  sun. 

Quadrilateral  Figure  — One  that  has  four  sides. 

Quartilc. — Ninety  degrees  distant  from  each  other. 

Quiescent — At  rest ; not  in  motion. 

Jiadiation. — An  eniLssion  ofrays. 

Radius. — A straight  line  from  the  centre  of  a circle  or  sphere  to  its  circumference. 

Radius  Vector. — A straight  line  between  a planet  and  the  sun,  or  centre  of  motion. 

Rahi. — Drops  of  water  falling  from  the  clouds. 

Refection.- -The  turning  back  of  rays  of  light  or  sound  from  a surface 

Refraction. — The  breaking  or  bending  of  a ray  of  light  in  passing  through  media  of  different 
densities 

P.^pulsion. — The  property  by  which  bodies  recede  or  fly  from  each  other 

li/tro^rnde  Motion  oj  a Planet. — Apparent  motion  from  east  to  west,  contraiy  to  the  order  of  the 
signs. 

Revolution. — Motion  from  a point  round  to  the  same  again. 

Risht  Ascension  — The  distance  east  on  the  equinoctial  from  the  first  point  of  Aries. 

R4oht  Line — A straight  fine  ; a direct  conirse. 

Roman  Indiction. — A period  of  13  years. 

Rotation. — The  motic^n  of  a l>ody  round  its  axis 


Satellite — A moon,  or  secondary  planet. 

Sroi^io. — The  eighth  sign  of  the  ecliptic. 

Seco7idai‘y  Circles. — Such  as  are  in  planer  that  ore  perpendicular  to  those  circles  of  which  they 
arc  the  secondaries. 

Sector  of  a CtVe/e. —Space  enclosed  by  tv  o ladii  and  an  arc,  less  tlian  a Bcmicirclo. 

Secular  Inequalities. — Variations  in  the  motions  of  the  heavenly  bodies,  requiring  many  ages  for 
their  accomplishment. 

Se^7nent. — Any  part  of  the  surface  of  a circle  cut  off*  by  a cord. 

Semicircle. — Half  a circle  Half  of  the  circumfcience,  or  an  arc  of  ISO  degrees 

Sideroal  Day. — The  time  included  between  two  consecutive  transits  of  the  same  star  at  the  same 
meridian.  'J’hi.s  period  is  invariably  of  exactly  the  same  continuance  ; and  it  is  the  only  one  in 
nature,  with  whioli  wc  are  acquainted,  that  is  so  Hence  it  forms  a perfect  standard  measure,  by 
reference  to  which  all  portions  of  lime  may  be  ascertained  Astronomical  clocks  are  made  to 
show  sidereal  time.  It  may  likewise  be  observed  that  our  standard  measures  of  length,  capacity, 
and  weight,  depend  upon  the  equable  rotation  of  tlie  earth  on  its  axis,  as  they  are  referred  to  tho 
length  of  a pendulum  beating  seconds  of  mean  time.. 

Siitn. — Thirty  deuces,  or  the  12th  part  of  a circle.  The  ascending  signs  of  the  ecliptic  are  tliose 
in  which  the  sun’s  meridian  altitude  is  daily  increasing. 

Snow. — Water  frozen  while  in  the  form  ol  clouds,  mist,  or  fine  rain,  which  then  falls  gently  to 
the  earth. 

Solar  Day. — The  time  from  one  noon  to  the  next,  is  the  apparent,  and  the  average  time  of  that 
period,  the  mean,  solar  day. 

Solar  System. — The  sun,  with  its  planets  and  comets  arranged  regularly,  in  their  several  positions. 

The  times  at  which  the  sun  is  in  the  soUtitial  points  When  the  sun  is  at  the  summer 
solstice  all  places  in  the  northern  hemisplicre  have  tlieir  longest  day.  These  day.s  vary  in  length 
fiom  12  hours  at  the  equator  to  24  at  the  arctic  circle,  and  in  the  frigid  zone  tliey  increase  from  24 
hours  at  the  arctic  circle  to  6 months  at  the  pole,  where  there  is  but  one  day  and  night  during  the 
year.  At  the  same  time  all  places  in  the  southern  hendsj.here  have  their  shortest  day,  7'hese  vary 
Irom  12  hours  at  the  equator  to  nothing  at  the  antarctic  circle,  where  the  sun  does  not  rise  above 
the  horizon.  The  length  of  the  days  in  south  latitude  corresponds  to  the  length  of  the  nio/its  in 
north  latitude  ; and  the  length  of  the  nishts  in  south  latitude  corresponds  to  the  length  of  the  days 
in  nortli  latitude  When  the  sun  is  at  the  winter  solstice,  this  condition  of  things  is  rever.sed,  and 
the  southern  hemisphere  presents  the  same  phenomena,  w'ith  respect  to  the  sun,  a.s  does  the  nortli- 
ern  when  the  sun  is  at  the  summer  solstice. 

Solstitial  Points. — The  points  of  the  ecliptic  which  are  farthest  from  the  equinoctial. 

South. — That  point  of  the  horizon  which  is  directly  oppo.site  to  the  nortli  pole 

Sphere. — A globe  or  hall.  .A  solid  whicli  has  every  point  of  its  surface  equally  distant  from  its 
centre.  Also,  the  concave  expanse  of  the  heavens  that  surrounds  Uie  qarlh  The*  sphere  lias  three 
positions,  right,  oblique  and  parallel  Those  who  live  at  tlie  equator  have  a right  .i^phere,  all  the 
circles  of  daily  motion  rising  directly  above,  and  descending  directly  below  the  horizon  Those 
who  live  between  the  equator  and  poles  have  an  oblique  sphere,  all  the  circles  of  daily  motion 
being  oblique  to  the  horizon.  Were  any  one  at  either  of  the  poles  he  would  have  a jiarallel  spliere, 
all  the  circles  of  daily  motion  being  parallel  to  the  horizon  On  4he  artificial  globe  a riglit  sphere 
is  represented  by  placing  both  poles  in  tho  horizon  ; an  oblique  sphere  by  raising  one  pole  h little 
and  depre.ssing  the  other ; a parallel  sphere,  by  bringing  one  pole  to  tho  zenith  and  the  other  to  the 
nadir. 

Sphei'ical  — Having  the  form  of  a sphere. 

Spheroid  — A solid  resembling  a sphere.  If  the  polar  diameter  be  the  least,  it  is  called  an  oblate 
spheroid  ; if  it  be  the  greatest,  it  is  called  a prolate  or  oblong  siiheroid. 

Spnng  Tide. — The  greatest  flood  and  ebb  tide 

Stationary. — A term  applied  to  the  apparent  motion  of  a planet,  wlicn  its  real  motion,  combinod 
with  that  of  the  earth,  causes  it  to  remain  at  the  same  point  in  tiie  heavens. 

Supplement  of  a7i  are  or  aneU. — V\’hat  the  arc  or  angle  wants  of  180  degrees. 

Suiface  — Tffat  which  has  length  and  breadth,  but  no  thickness. 

Synodic  Month — .A  complete  lunation,  or  from  one  new  moon  to  another ; it  being  39  davs,  12 
hours  and  44  minutes.  . 

Syzygies  — The  points  in  the  moon’s  orbit  where  she  is  new  or  full. 

Taui'us. — The  second  sign  of  the  ecliptic. 

7Vrf«.— The  rising  and  falling  of  the  waters  of  the  ocean.  The  rising  of  the  water  is  called  flood 
tide  ; the  falling,  ebb  tide. 

Transit — Tlie  passage  of  a body  acro.ss  the  meridian  of  a place.  The  transit  of  Mercury  and 
Venus  usually  means  their  apiiarcnt  passage  across  the  sun’s  disc. 

Trapezium. — A figure  bounded  by  four  unequal  sides. 

Tiiangle. — A figure  bounded  by  three  lines,  or  sides.  An  equilateral  triangle  has  three  equal 
sides ; an  iso.^celes,  only  two  ; a scalene  triangle  has  three  unequal  sides.  A triangle  is  called  a 
ri^t,  obtuse,  or  acute  angled  triangle,  according  as  it  has  a right,  obtuse,  or  three  acute  angles. 

Tropic  of  Cancer. — .A  small  circle.  23*^  28'  north  of  the  equator,  and  parallel  to  it. 

T,  ofic  of  Capi'icoi'n. — A small  circle,  2.3®  2S'  south  of  the  equator,  and  parallel  to  it. 

Tropical  Year. — The  period  between  the  consecutive  returns  of  the  .sun  to  the  same  tropic  or 
solstice. 

True  Distance — The  actual  distance  of  a body  from  the  sun,  or  of  a satellite  from  its  planet. 

7V«e  Place  of  a Planet. — 7'he  place  where  it  would  appear  to  be,  if  seen  from  the  centre  of  llie 
earth,  or  centre  of  inotioti. 

Twilight. — The  faint  light  of  the  sun  before  sunrise  and  after  sun-set. 

Umbra. — A dark  or  total  shadow. 

Universe — The  whole  material  creation.  It  has  been  improperly  applied  sometimes  to  large 
clusters  of  stars. 

I'apor. — VV'ater  in  an  ceriform  state— steam. 

Vertex. — The  head,  top,  or  summit. 

Vertical. — The  direction  of  the  plumb-line. 

Vertical  Plane.— A plane  passing  through  the  plumb-line,  consequently  perpendicular  to  the 
horizon 

Vertical  Circle. — A circle  in  a vertical  plane,  passing  through  the  zenith  and  nadir,  and  cutting 
the  horizon  at  right  angles 

Virgo  — 7'he  6tn  sign  of  the  ecliptic. 

H unmg. — Declining  in  power,  or  decreasing  in  light. 

iresb— That  direction  in  which  the  snn  sets  when  in  the  equinoxes. 

in  motion.  The  trade  winds  blow’  steadily  to  the  westward,  in  the  Atlantic  and 
Pacific  oceans,  between  the  tropics.  The  monsoons,  or  shifting  trade  w-inds,  in  the  Indian  oceau. 
blow’ part  of  the  year  oneway,  and  the  other  part  in  an  opposite  direction.  The  winds  l)oyond 
the  40th  degree  of  latitude  are  all  variable.  In  the  torrid  zone,  near  the  sea,  breezes  blow  from  the 
land  in  the  morning  and  from  the  sea  in  the  evening. 

solar  or  trojiical  year  is  the  period  from  the  departure  of  the  sun  from  the  summer  sol- 
stice, to  its  return  to  it  again.  U*!  lengtli  is  365  days,  6 houis,  and  nearly  49  minutes.  The  sidereal 
year,  which  is  the  period  between  the  departure  and  return  of  the  sun  to  a fixed  star,  is  about  17 
minutes  longer.  The  aiiomalislical  year  is  the  time  from  the  sun's  leaving  his  apogee  till  lie 
returns  to  iti  and  is  36.3  days,  6 hours,  and  about  14  minuses 

Ze7iith— The  point  in  the  heavens  directly  over  head. 

Zenith  Distance — The  angular  distance  of  a heavenly  boa  fiom  the  zenith,  measured  on  a verti- 
cal circle. 

Zodiac. — A space  or  belt  in  the  heavens.  16  degrees  broad,  on  each  side  of  the  ecliptic.)  in 
which  are  the  orbits  of  all  the  planets  except  a part  of  t!ie  astcro.Js. 

Zone.— A belt  or  girdle  on  the  earth’s  surface,  formed  by  circles  parallel  to  the  equator  7'here 
are  five  zones  ; the  torrid,  Iw’O  temperate,  and  two  frigid,  formed  by  the  tropics  and  polar  circles 


j 


TOWER’S  SERIES  OF  SOIIOOE  ROOKS, 

1‘UllMSIIED  BY 

DAOTEIi  BURGrESS,  CO.  60  JOHN-STREET,  HEW  YORK. 


Gradual  Primer.  First  Book. 

The  merits  of  this  book  consist, — 

1.  In  coupling  letters  by  tlieir  resemblancrs. 

2.  In  giving  only  a few  letters  of  the  alphabet,  before  »cor,/.»  are  given  com- 
posed solely  of  those  few  letters. 

n.  In  giving  only  07ie  7W7vet  in  a lesson,  with  coords  which  contain  the  name, 
sojin-d  of  that  vowel.  This  is  a new  and  peculiar  method  of  leaching  tlie  alphabet, 

•1.  In  considering  the  several  powers  of  each  ttowel  in  a separate  lesson,  with 
easy  words,  and  short,  plain  sentences,  to  illustrate  each  individual  power  or 
sound ; thus  teaching  only  one.  thing  at  a time. 

5.  The  diphthongs  or  combined  vowels  are  taught  in  the  same  manner. 

6.  Each  Consonant  clement  is  then  considered  by  itself,  in  a separate  les- 
son, with  easy  words  and  sentences,  for  exercise  on  its  particular  sound. 

T.  Particular  and  specific  directions  are,  for  the  first  time,  given  to  teach- 
ers, for  uttering  each  elementary  sound  in  the  language.  * 

8.  More  general  directions  or  suggestions  arc  also  given  for  teachers. 

Tables,  peculiar  to  this  Series  alone,  are  inserted  for  daily  practice  of  classes 
simultaneously  in  all  the  simple  elementary  sounds. 

These  are  the  jirominent  features  of  this  Primer,  and  are  peculiar  to  it  alone. 
The  teacher,  as  well  as  the  pupil,  will,  from  its  use,  lay  the  foundation  of  a 
distinct  articulation,  and  be  saved  from  much  expense  of  time  and  labor  in 
unlearning.  This  is  “the  right  step  taken  in  the  right  place.” 

Introduction  to  the  Gradual  Header.  Second  Book. 

The  peculiarities  of  this  book  consist, — 

1.  In  taking  the  pupil  gradually  through  all  the  easier  consonant  com- 
binations, by  a regular  progressive  exercise  on  each  combination. 

2.  Through  all  the  points,  or  marks  used  by  writers,  illustrating  each  in  a 
separate  lesson 

3.  Through  all  the  simple  slides  of  the  voice,  in  the  .same  manner. 

4.  Progressive  reading  lessons,  adapted  to  the  progress  of  tlie  pupil. — The 
reading  lessons  are  kept  entirely  distinct  from  the  lessons  in  articulation,  points, 
&.C.,  that  only  one  thing  may  be  taught  at  a time,  as  in  the  Primer,  which  it 
is  designed  to  follow. 

5.  Tables  for  daily  simultaneous  practice  of  the  elementary  sounds,  and  sim- 
ple combinations.  This  book  is  the  second  progressive  step  in  attaining  a dis- 
tinct utterance,  and  correct  pronunciation. 

6.  Suggestions  to  teachers  for  avoiding  errors  in  reading. 

Gradual  Reader.  Third  Book. 

This  book  contains, — 

1.  Such  a selection  of  reading  matter  as  will  interest,  as  well  as  instruct,  the 
learner,  progressively  suited  to  his  capacity. 

2.  A complete  and  original  system  of  articulation,  consisting  of  exercises 
upon  every  vowel  and  consonant  element,  and  upon  every  vowel  and  consonant 
combination,  in  the  language,  even  the  most  difficult.  This  was  the  first  ever 
published,  and  is  the  only  complete  system. 

3.  Tables  for  simultaneous  practice,  by  a whole  school,  on  all  the  elemen- 
tary sounds  and  their  combinations.  Since  the  publication  of  these  Exercises, 
in  1841,  the  subject  of  articulation  has  received  much  attention,  and  they  are 
said  to  have  done  more,  for  both  teacher  and  pupil,  in  making  good  readers, 
than  any  other  book. 

4.  d'he  Gradual  Reader  was  prepared  as  stated  in  the  preface,  on  the  plan  of  teach- 
ing only  one  thing  at  a time,  v.  plan  peculiar  to  this  book,  unless  copied  by  others. 

f).  The  exercise.s  '.Mokept  separate  from  the  reading  lessons,  that  the  whole 
school  at  once,  may  be  kept  daily  drilled  in  some  portion  of  them  previous  to  read- 
ing ; then  the  pupil’s  attention  will  not  be  continually  called  from  the  sentiment 
and  expression  of  a piece,  by  constant  interruption,  to  correct  his  articulation. 

6.  The  exercises  in  this  book  are  full,  to  supply  any  deficiency  in  the  elemen- 
tary instruction  of  advanced  pupils.  (See  printed  notices  of  the  book  and  system.) 

These  tliree  books  furnish  complete  and  thorough  instruction  in  articulation, 
the  groundwork  of  all  good  reading. 

N»  Second  Class  Reader.  Fourth  Book. 

1.  This  Reader  contains  an  elaborate  but  comprehensive  treatise  on  Elocu- 
tion, in  which  the  Jeading  principles  of  good  reading  are  simplified,  and  rules 
deduced  and  illustrated  by  jiractical  examples.  These  are  so  plain  that  the 
child  can  easily  cornprehitnd  them. 

2.  References  are  made  in  each  reading  lesson  to  some  of  the  principles  al- 
ready developed,  that  the  pupil  may  exercise  his  mind  by  the  practical  appli- 
cation of  the  same. 

3.  Each  lesson  has  its  partial  vocabulary,  to  exercise  the  pupil’s  judgment  in 
discriminating  and  selecting  the  definition  appropriate  to  explain  the  author’s 
meaning. 

4.  Above  a thousand  of  the  most  difficult  words  are  thus  practically  leixn- 
ed  ; and  the  pupil’s  knowledge  of  language  is  understandingly  enlarged. 

f).  Each  lesson  is  preceded  by  practical  exercises  in  enunciation,  exhibit- 
iug  the  correct  pronunciation  of  words,  and  the  distinct  utterance  of  simple 
clernenls  and  difficult  cornbii  .tions. 

ft.  These  exercises  may  e practised  simultaneously  previous  to  taking  up 
the  reading  b -.jon. 

7.  The  vele/tiions  have  been  carefully  made  in  reference  to  their  jirac.lical 
utility  and  interest,  and  their  adaptation  to  the  capacity  of  the  pupils  for  whom 
they  were  designed. 

N.  A.  First  Glass  Roador.  Flflk  Book. 

This  Reader  contains  a pliilosojihical  trenliie  on  the  highor  departments 


I of  Elocution.  In  this  treali.se  the  vocal  elements  are  treated  as  the  constit- 
uents of  speech.  Each  one  is  considered  in  an  insulated  light,  and  illustrated 
by  appropriate  exercises.  It  is  next  shown  how  these  constituents  are  applied 
in  combination,  in  every  instance  of  chaste  and  iinpa.ssioned  eloi|iiene,e  or  cor- 
corrcct  and  impressive  reading.  When  this  treatise  is  examined,  it  will  be  found 
that  the  whole  subject  is  clearly  illuslialed,  and  the  essential  points  are  arrang- 

1/  cd  in  such  a manner  as  to  be  easily  comprehended.  “ It  is  iny  firm  coiivielion,” 

says  one  of  the  most  accomplished  scholars  of  the  iireseni  day,  “ the  treatise 
on  elocution  and  principles  of  reading  as  illustrated  and  explained  in  the  North 
American  First  and  .Second  Class  Readers,  will  do  more  to  excite  the  atten- 
tion on  the  subject  of  language  and  reading,  than  any  thing  else  which  has  yet 
made  its  appearance  ; ami  were  I again  to  teach,  I should  by  all  means  exercise 
my  classes  on  the  illustrations  as  they  are  arranged  under  each  priiieiple.  The 
i selections  aro  excellent,  and,  if  merit  ho  recommendation  or  any  criterion 
i of  success,  these  books  arc  destined  to  be  more  extensively  used  than  any  other 

/ series  of  reading  books  which  has  yet  been  published.”  These  books  arc  now 

j pre.scntcd  to  the  public  without  agents  to  push  them  into  notice,  it  being  pre- 
j sumed  that  when  examined  they  will  meet  with  general  favor. 

> Gradual  Spoiler. 

} 1.  This  book  is  the  first  attempt  to  arrange  words,  in  separate  classes,  by  the 

j consonant  combinations — thus  aiding  the  memory  on  the  principle  of  association, 
j 2.  It  is  free  from  the  unmeaning  cuts  which  disfigure  most  books  of  the  kind, 

j and  furnish  a gratuitous  supply  of  jrlaythings  to  distract  the  attention 

( 3.  It  is  not  cumbered  with  reading  lessons,  useless,  because  out  of  place. 

< 4.  It  contains  an  exercise  on  each  consonant  element  as  well  as  each  vowel 

! element. 

s 5.  It  gives  also  an  exercise  on  each  consonant  combination  separately.  No 
S other  spelling-book  does. 

5 6.  It  gives  the  sound  of  each  vowel  in  every  word  ; without  which,  any  .Spel- 

I ling-book  would  be  worse  than  useless  in  a school. 

? 7.  The  sounds  of  the  vowels  are  indicated  by  a new  method  ; so  simple,  that 

? any  child  can  readily  master  and  use  it. 

j 8.  The  same  notation  answers  for  the  diphthongs,  which  is  an  advantage 

l over  any  other  plan. 

< 9.  As  each  element  and  each  combination  is  considered  in  a separate  exer- 

t cise,  the  book  is  a great  collateral  aid  to  articulation,  while  it  gives  the  correct 

t pronunciation  in  connection  with  teaching  the  orthography  of  the  language. 
Intellectual  Algebra. 

This  is  on  a new  and  original  plan,  and  is  the  first  attempt  to  simplify  and 
illustrate  this  science,  that  it  may  be  taught  orally.  As  a discipline  of  the  mind 
in  teaching  the  pupil  to  think  and  reason , a\gehTa.  is  pre-eminent;  and  this 
work  places  it  in  the  power  of  younger  classes  to  be  benefited  by  such  mental 
exercise.  Where  it  has  been  used,  it  has  more  than  answered  the  high  ex- 
pectations of  teachers. 

1.  The  processes  are  so  divided  and  subdivided  as  to  present  but  one  thing 
at  a time  to  the  learner,  and  that  in  its  simplest  form. 

2.  The  operations  are  limited  to  small  numbers,  so  as  not  to  embarrass  the 
reasoning  powers. 

3.  The  pupil  is  led  gradually  from  the  simplest  to  more  complicated  reasoning. 

4.  Though  not  designed  for  that  purpose,  it  has  been  used  successfully  as  a 
text-book  for  written  algebra, 

A Complete  Key  to  the  Algebra. 

This  book  contains  explanations  and  solutions  to  all  the  questions  in  the 
Algebra,  for  the  convenience  of  teachers,  and  for  their  use  only. 

Gradual  Lessons  in  Grammar. 

1.  It  is  based  entirely  on  the  analysis  and  composition  of  sentences  ; and 
its  exercises  are,  consequently,  from  the  very  beginning,  entirely  of  a practi- 
cal character. 

2.  The  .st/ftyect  mAihe  predicate  of  each  proposition  are  ybei  modified  or 
limited  by  all  other  words  therein. 

3.  The  pupil  must  not  only  know  the  meaning  of  each  word,  but  how  it 
affects  the  meaning  of  the  general  proposition. 

4.  Besides  the  abstract  power  of  words,  the  local  value  will  also  be  eradually 
acquired  from  observing  their  modified  influences  as  they  are  variously  used. 

5.  Lartguage  is,  in  this  way,  both  regarded  and  studied  as  the  medium  of 
thought. 

6.  The  two  principal  parts  of  a proposition  must  first  be  found  ; then  how 
each  is  modified  by  the  several  words  that  cluster  around  it ; and  thus  how  the 
meaning  of  the  part  or  the  whole  is  affected  thereby.  This  is  an  invaluable 
exercise  of  the  understanding. 

7.  Then  the  pupil  is  required  to  analyze  compound  sentences,  till  the  con- 
nection or  dependence  of  clauses  is  rightly  understood,  with  their  limiting 
or  modifying  power. 

8.  Sentences  are  thus  analyzed  and  constructed,  and  the  relations  of  words 
and  clauses  comprehended,  with  the  limiting  force  of  each,  before  the  minor 
distinctions  and  the  technicalities  are  introduced. 

9.  The  plan  is  new,  and  pleases  every  enlightened  teacher  who  examines 
it.  The  pupil  is  taught  to  compose  as  well  as  analyze. 

Teachers  say  that  this  Grammar  ojjcns  a new  path  for  the  pupil,  enabling  him, 
to  pursue  this  sometimes  dry  study  not  only  understandingly,  but  with  interest 
and  pU  isure.  It  is  predicted  of  the  “ Lessons,”  that  they  will  produce  as  great  a 
5 change  in  the  method  of  teaching  grammar,  as  Colburn’s  “ First  Lessons”  did 
I in  arithmetic. 


I 

f' 


t 


ACKERMAN’S  NATURAL  HISTORY, 

288  pnges,  12i  lo.,  half  bouiui  . . . . 

A.'MERIC  \\  EXPOSITOR, 

or.  Intellectual  Deliiier. — by  R.  Clagijjtt,  A.  M.  - 

ELOCUl’ION  MADE  EASY, 

By  R.  Claggett,  A.  M ... 

GUERNSEY’S  il  STOR\  OF  THE  UNITED  S'I'ATES, 
450  pages,  i2i  \o.,  half  bound, 

■“  “ *'  “ “ cloth. 

B-S  R.  C.  SMITH,  A.  M. 

SMITH’S  INTRODUCTORY  ARlTHME'riC, 
or.  First  Cook  in  Arithmetic,  ISmo.  - 
vHTH’S  PRACTICAL  AND  MENTAL,  " ^ 

or.  Second  Book  in  Arithmetic — 288  pages,  18mo. 

S.  ilTH’S  KEY  TO  “ . . 

S.MITH’S  NEW  ARITHMETIC, 

or,  Third  Book  in  Arithmetic — 312  pp.,  12mo.  half  bound. 

SMITH’S  KEY  TO  » . . . . 

SMITH’S  FIRST  BOOK  IN  GEOGRAPHY, 

Revised  Edition.  - .... 

S.MITH’S  4to.,  OR  SECOND  BOOK  IN  GEOGRAPHY’, 
or.  Sequel  to  the  First  Book.  - - - - 

SMUriJ’S  GEOGRAPHY  AND  ATLAS, 

or,  Third  Book.  - - - - • i - 

BY  ASA  SMITH. 

S.MITH'S  ILLUSTRATED  ASTRONOMY, 
in  quarto  form,  illustrated  with  28  diagrams. 

SMH'H’S  ABRIDGED,  “ “ . . . 

72  pages,  12mo.,  with  plates.  ... 

TOWER’S  SERIES. 

GRADUAL  SPELLER, 

and  Complete  Enunciator — 100  pages,  12mo. 

GRADUAL  PRIMER, 

or,  'PoM-er’s  First  Book — 72  pages,  18mo. 

INTRODLtl'PION  TO  GRADUAL  READER, 
or,  'J'owor’s  Second  Book — 180  pages,  18tno. 

GRADUAL  reader, 

or,  To.ver’s  Third  Book — 108  pages,  12mo. 

INTERMEDIATE  READER, 

108  (lagei,  12mo.  ..... 

NORTH  AMERICAN  HECOND  .CLASS  READER, 

tir,  'I'ower’s  I'nurth  Book — Ijv  D.  B.  'J'ower  and  Oornelius 
Walker,  288  pages,  12mo.,  cloth. 

NORTH  AMI'.RICAN  FIRST  CLASS  READER, 

or,  'Power's  Fi.'lh  Book — by  I).  B.  'Power  and  Cornelius 
Walker,  432  pagr-i,  12mo.,  sheep. 


GRADUAL  LESSONS  IN  ENGLISH  GRAMMAR, 

with  Si'quel — by  D.  B.  Tower  and  BenJ.  1’.  'Pweed,  288 
pa",!8,  12mo.  ...... 

I N 'P  E L L 1 : C'P  U A » , A I A I E P R A , 

or,  Or.il  F,  icises  in  A'e^h-a--ff>r  Common  Schools,  by 
D.  B.  'Power,  210  [lage?  12  no.  - - 

KEY  'PO  “ “ . . . 

MISCELLANEOUS. 

LA  FEVER’S  MODERN  BUILDER’S  GUIDE, 

new  and  improved  edition. — (piarto,  sheep. 

BANNING  ON  CHRONIC  DISEASFIS,  pajrer.  - 
. “ “ “ “ muslin. 

SAWYF.R’S  MENTAL  PHILOSOPHY', 

by  LEit’vsTKK  S.xwYEK,  bite  of  Central  College,  Ohio. — 
Designed  for  Schoolr  and  Academies. — 12mo.,  cloth. 
CATECHISM  OF  CHRIS'PIAN  MORALS, 


by  L.  A.  Sawyeh,  A.  M. 


muslin. 

paper. 


WATER-CURE  MANUAL, 

12mo.,  by  Joel  Shew,  M.  D. — cloth. 

“ “ paper. 

OVER  THE  OCEAN; 

or.  Glimpses  of  Travel  in  Many  Lands. — By  a Lady  of 
New  Y'ork ; 1 vol.  12mo.,  paper. 

“ “ “ “ “ “ cloth. 

IVES’  MUSIC  BOOKS. 

MUSICAL  ABC,  with  SONGS  TO  SWEETEN  ^TUDY. 
by  E.  Ives,  Jr.  - . - 

THE  MUSICAL  SPELLING  BOOK, 

a New  Method  of  Instruction  and  Musical  Recreation. — 
8vo. ; by  E.  Ivr.s,  Jr. 

THE  MOZART  COLLECTION  OF  SACRED  MUSIC, 
containing  Melodies  and  Chorals,  set  to  fifty  different  metres. 
Also,  the  celebrated  Christus  and  Miserere,  with  the  adapta- 
tion of  English  words ; to  which  is  prefixed  the  New’  Method 
of  Teaching  the  Rudiments  of  Music. — by  R.  Jves,  Jr. 

THE  MUSICAL  READER, 

a-New  ."lethod  of  Instruc'’  : , ; .kI  Music,  Sacred  and  Se- 
cular. Designed  for  Sci'  Js  and  Masical  .Academies. — by 
E.  Ives,  Jr.  ...... 

THE  BEETHOVEN  COLLE(;TiON  OF  SACRED  .MUSIC 
— comprising  Themes,  now  first  arranged  from  the  Instru- 
mental compositions  of  Beetbo'cn,  Hyden,  Mozart,  and 
other  eminent  Composer.s,  and  Origins’  'Punes,  Chants,  and 
Anthems;  the  whole  harmoni'cd.  in  four  parts,  with  an 
Accompaniment  for  the  Organ,  by  Messrs.  Ives,  Aleeus, 
and  'Pimm.  ...... 

MUSICAL  WREA'PH,  by  E.  Ives,  Jr. 

“ “ “ “ gilt  edge.  - 


